J 



-'f 












> ' .r'v 



V 



f4 









■ , 1. * ,0 



>- 














''-J ^rf:\ 










,x^' '^r. 




c^' 



/ -^ - /JV^, 



oo^ 






A -n. 



AMERICAN SCIENCE SERIES, ELEMENTARY COURSE 



THE ELEMENTS 



OF 



CHEMISTRY 



A TEXT-BOOK FOR BEGINNERS 



BY 

lEA EEMSEN 

President of the Johns Hopkins University 



SECOND EDITION, REVISED 






.,,,».' ••• 



NEW YORK 

HENRY HOLT AND COMPANY 
1902 



T^fxTBRARYOr 

CONGRESS, 
Two Comes Rgccived 

AUG. 9 1902 

CLASS ^ XXa Ho. 

3 f OS'S 

COPY B. 



Copyright, 1886, 1902, 

BY 

HENRY HOLT & CO. 



ROBERT DRUMMOND, PRINTER, NEW YCRK 






^ 



^- 



r 



7 ^ 



PREFACE. 

This book is written upon much the same plan as the 
Briefer Course in the same series. -It is^ however^ mate- 
rially simpler in many parts^ and is in every way better 
adapted to younger pupils. In "the opinion of the author 
a rational course in chemistry^ whether for younger or 
older pupils^ is something more than a lot of statements 
of facts of more or less importance; a lot of experiments 
of more or less beauty; or a lot of rules devised for the 
purpose of enabling the pupil to tell what things are made 
of. If the course do'cs not to some extent help the pupil 
to think as well as to see^ to reason as well as to observe, 
it does not deserve to be called rational. Not only must 
the pupil perform experiments, but he must know why he 
performs them, and what they teach. A good plan to 
follow is to talk over a certain part of the subject, show- 
ing how to construct the apparatus necessary for some of 
the experiments, and stating in a general way what is to 
be learned; then to let the pupil perform the experiments 
with the aid of the book and the teacher; and afterwards 
to make the experiments the basis for questioning. In 
this way the pupil will become observant, and at the same 
time he will discover when his experiments have been 
performed in the wrong way. It is better to go slowly at 



IV PREFACE. 

first so as to allow the pupil time to become familiar with 
his surroundings and to enable him to learn how to work 
at the laboratory desk. A badly constructed piece of ap- 
paratus or an experiment badly performed in any way 
should not be allowed to pass. Experiments should be 
repeated as many times as may be necessary to secure 
accurate work. 

Chemical theories are treated in a subordinate way, as 
it is believed that the attention should first be directed to 
the simpler facts of the subject and the methods by which 
these facts are learned. A brief statement of a few of the 
prevailing hypotheses is given in Chapter XIY. Whether 
it will be advisable for the pupils to spend any time in 
studying this chapter will depend upon their age and their 
mental attainments. If all they can do is to learn the 
statements by heart and repeat them without showing any 
signs of comprehension, then unquestionably the chapter 
should be omitted. It should be remembered that the 
object of the course laid down in this book is not to make 
chemists, but to help to develop sound minds, and at the 
same time to awaken interest in a set of natural phenom- 
ena of great importance to mankind. It is quite possible 
to teach the subject in such a way as to destroy all in- 
terest in chemical phenomena and to make the pupil 
shudder whenever a chemical formula is mentioned. 
There is no better way to accomplish the latter result 
than by giving prominence to incomprehensible theories 
and forcing the pupils to master a lot of equations which 
represent facts of which they are entirely ignorant. 
Johns Hopkins University, December 27, 1886. 



PREFACE TO SECOND EDITION. 

This book has been thoroughly revised^ and it is be- 
lieved that all necessary or desirable changes have been 
made. 

The author desires to thank Dr. C. E. Waters, of the 
Johns Hopkins University, for many valuable suggestions 
and for his conscientious reading of the proof. 

I. R. 

Johns Ho:pkins University, June 2, 1902. 



CONTENTS. 

CHAPTEE I. 

PAGE 

Chemical Changes — Physical Changes 1 

CHAPTER II. 
The Chemistry of the Air <. 17 

CHAPTER ni. 
Oxygen 22 

CHAPTER IV. 
Combining Weights ^ . 32 

CHAPTER V. 
Nitrogen 39 

CHAPTER YI. 
Water . . 44 

CHAPTER VII. 
Hydrogen «... 48 

CHAPTER YIII. 
Water (continued) 56 

CHAPTER IX. 

Compounds of Nitrogen with Hydrogen and Oxygen ... 71 

vii 



via CONTENTS. 

CHAPTER X. 

PAGE 

Chlorine and its Compounds with Hydrogen and Oxygen . . 83 

CHAPTER XL 
Acids — Bases — Neutralization — Salts 94 

CHAPTER XII. 
Carbon 105 

CHAPTER XIII. 

CompoTinds of Carbon with Hydrogen, with Oxygen, and with 

Nitrogen 116 

CHAPTER XIV. 

Atomic Theory — Atomic Weights — Molecular Weights — Val- 
ence — Classification of the Elements 135 

CHAPTER XV. 
The Chlorine Family: Chlorine, Bromine, Iodine, Fluorine . 143 

CHAPTER XVI. 

The Sulphur Family: Sulphur, Selenium, Tellurium . . . 150 

CHAPTER XVII. 

The Nitrogen Family: Nitrogen, Phosphorus, Arsenic, and 

Antimony — Boron and Silicon 164 

CHAPTER XVIII. 
Base-forming Elements — General Considerations . . . . . 173 

CHAPTER XIX. 
The Potassium Family: Potassium, Sodium, (Ammonium) . 177 



CONTENTS. IX 

CHAPTER XX. 

PAGE 

The Calcium Family: Calcium, Barium, Strontium .... 190 

CHAPTER XXI. 

The Magnesium Family: Magnesium, Zinc, Cadmium — The 

Copper Family: Copper, Mercury, Silver 198 

CHAPTER XXII. 

The Aluminium Family — The Iron Family: Iron, Cobalt, 

Nickel 209 

CHAPTER XXIII. 
Manganese — Chromium — Uranium-^Bismuth 219 

CHAPTER XXIV. 
Lead — Tin — Platinum — Gold 222 

CHAPTER XXV. 
Some Familiar Compounds of Carbon » , . 229 

CHAPTER XXVI. 
Other Compounds of Carbon 244 

Questions and Problems 256 

Index 281 

Weights and Measures 3d cover page 



APPAEATUS AND CHEMICALS. 

For the benefit of those who have no laboratory at com- 
mand, and who may wish to make arrangements for going 
through with the experimental work, the following list has. 
been drawn np. In it is included everything necessary to 
perform the experiments on a small scale. Should it be 
desired to fit up a room with conveniences for students, the 
amount of apparatus necessary would depend upon the 
number of students, but for each individual the expense 
Avould be small, as many of the pieces of apparatus, such as 
the galvanic battery, burettes, weights, scales, etc., need not 
be multiplied. In place of some of the pieces of apparatus 
described in the book, ordinary kitchen utensils will answer: 
thus, for example, instead of the trough for collecting 
gases, a tin pan or a deep earthenware dish may be used ; 
instead of the water-bath, a stew-pan, fitted with two or 
three different-sized tin or sheet-iron rings; and in place of 
glass cylinders for working with gases, wide-mouthed cheap 
bottles. 

The publishers do not deal in chemicals and apparatus, 
nor, they may as well say, receive commissions on them. 
Any orders should be sent direct to the dealers. 

Messrs. Eimer & Amend, Nos. 205 to 211 Third Avenue, 
New York, whom the publishers take the responsibility of 
recommending as thoroughly reliable, will furnish each of 
the following articles at the price given. 

If several pieces of the apparatus in List No. 1 are taken, 
a discount of 10 per cent will be made; on a complete set 
20 per cent discount will be allowed; on three or more sets, 
25 per cent. 

One or more of the articles in List No. 2, if not marked 
^^net " or ^'^ 10 per cent," will be supplied at 20 per cent 
discount if ordered with sets of the apparatus in List No. 1. 



APPARATUS AND CHEMICALS. 



XI 



A discount of 10 per cent will be given on a complete 
set of tlie chemicals, and of 15 per cent on three or more 
sets. 

For most items less than the whole set, there will have 
to be a small additional charge for packing. It should be 
realized, however, that usually the charge for packing one 
article must be as large as for several. Some articles can, 
of course, be mailed without any charge for packing. 



List Xo. 1. 

A list of apparatus and chemicals necessary for performing all 
of the experiments in Remseu's Elements of Chemistry, with the 
exception of experiments Xos. 34, 36, 46, 47, 48, 49, 51, 65, 66, 80, 
81, and 113. To perform these latter experiments, the apparatus 
given in List No. 2 is required. 



APPARATUS, 

1 Nest Beakers, 1-3 $0 35 

1 Jeweller's Blowpipe, Sin 10 

7 Wide-mouth Flint Bottles, two 

each, 2, 4, 8 oz., and one 32 oz. 40 
1 Bunsen's Burner with regula- 
tor, or 6 oz. glass alcohol 

lamp, same price 40 

1 5-in. U tube 25 

1 Set Cork Borers, 1-6 1 00 

1 Dropping-funnel, 50 c.c 1 00 

2 doz. Assorted Corks. 20 

1 Nest Hessian Crucibles, 

'' threes " 5 

2 ]^-in. Porcelain Crucibles 36 

1 25 c.c. Grad. Cylinder 35 

I Deflagrating Spoon 15 

1 each Evaporating Dish, 2^^ and 

3i^in 35 

1 Lead Dish, 2 in 12 

1 Round File, 5 in 20 

1 Triangular File, 5 in 20 

1 Pack White Filters, 4 in 13 

4 Flasks : one 4 oz., two 8 oz., 

one 16 oz 65 

1 Steel Forceps 20 

2 Funnels, 21^ in 24 

2 Funnel Tubes, one 10 in., one 

15 in 25 

1 Gas Bottle, 8 oz., with 2-hole R 

Stopper 30 

\^ lb. Assorted Glass Tubing, 4-7. 25 

\i lb. Assorted Glass Rods 15 

2 Sheets each Red and Blue Lit- 

mus-paper 20 

1 Horseshoe Magnet, 3 in 12 

1 Porcelain Mortar and Pestle, 

33^ in 45 

1 Piece Platinum Foil, 1 x li^ in . . 1 00 

6 in. Medium Platinum Wire 50 

1 Plain Retort, 8 oz 22 



1 Stoppered Retort, 16 oz $0 45 

3 ft. Rubber Tubing for gas, 34 in. 39 

(Only needed if Bunsen's 
Burner is used.) 

2 ft. Rubber Tubing (for connec- 

tions) 20 

1 33^ in. Sand Bath 15 

1 Hand Scale, with weights 85 • 

1 Test Tube Stand 30 

12 Test Tubes, 5 in 30 

] Tes-t Tube Brush 5 

1 Test Tube Clamp 15 

1 Iron Tripod 30 

1 Filter-stand (2 rings) 45 



1 Wire Triangle., 

1 Piece Wire Gauze, 6 x G in 

1 Piece Blue (3rlass, 2x2 in 

1 Piece Ground Glass, thin, 4x4 

in 

2 2-in Watch-glasses 

1 5-in. Water-bath., 



5 

10 
10 



10 
90 



2 Wire Clamp Supports 1 60 



$16 64 
CHEMICALS. 

4 oz. Acid Acetic, pure (bottle 5 

cents extra) $0 10 

4 oz. Acid Arsenious. , 10 

16 oz. '" Hydrochloric (bottle 

15 cents extra) 10 

8 oz. Acid Nitric (bottle 12 cents 

extra) 10 

2 oz. Acid Oxahc 10 

16 oz. '* Sulphuric (bottle 12 

cents extra) 10 

1 oz. Acid Tartaric 10 

2 oz. Alcohol, for experiments 

only (bottle 4 cents extra). . . 10 

8 oz. Alum 10 

4 oz. Ammon. Chloride 10 



Xll 



APPARATUS AND CHEMICALS. 



8 oz. Ammon. Hydrate, concen- 
trated (bottle 10 cents extra). SO 10 

4 oz. Ammon. Nitrate 10 

2 oz. Antimony, powdeied 10 

2 oz. " and Potassiun. 

Tartrate 20 

2 oz. Barium Chloride 10 

4 oz. Calcium Chloride, fused.. . 10 
1 oz. " Carbide (bottle 3 

cents extra) 10 

4 oz. " Sulphate 10 

4 oz. Carbon Bisulphide (bottle 5 

cents extra) 10 

8 oz. Animal Charcoal, powdered 10 

8 oz. Copper Foil 20 

4oz. " Sulphate 10 

1 oz. " Oxide 15 

4 oz. Fluor spar, powdered 10 

1 oz. Indigo 10 

1 oz. Iodine (bottle 2 cents extra) 30 

4 oz. Iron Filings, fine 10 

8oz. " Sulphide 10 

4 oz. " Sulphate 10 

4 oz. Lead Sheet 10 

4 oz. " Acetate 10 

2oz. " Nitrate 10 

1 oz. " Peroxide 10 

2 oz. " Sesquioxide 10 

1 oz. Litmus 10 

J^ dram Magnesium Ribbon 10 

,1 lb. Manganese Dioxide, pow- 
dered....... 10 

1 oz. Mercury Red Oxide 10 



1 oz. Nutgalls, powdered $0 10 

2 oz. Paraffin 10 

1 oz. Phosphorus (bottle 10 cents 

extra) 1.5 

1 dram Potassium 30 

2 oz. " Bromide .. 10 

4oz. " Carbonate 

(bottle 5 cents extra) 10 

4 oz. Potassium Chlorate 10 

4 oz. " Bichromate 10 

2 oz. " Ferricyanide. . . . 10 

4 oz. " Hydrate Sticks 

(bottle 5 cents extra) 20 

1 oz. Potassium Iodide (bottle 5 

cents extra) 25 

4 oz. Potassium Nitrate 10 

2 oz. " Permanganate.. 10 

1 dram Sodium (bottle 3 cents 

extra) . 10 

2 oz. Sodium Acetate, fused 10 

2 oz. *' Bicarbonate 10 

4 oz. " Biborate (Borax) . . 10 
4 oz. " Hydrate (bottle 5 

cents extra) 20 

4 oz. Sodium Nitrate 10 

4 oz. " Sulphate. 10 

8 oz. Sulphur, roll 10 

4 oz. Tin, granulated 10 

16 oz. Zinc, granulated 20 

2oz. *' Sulphate 10 

$8 36 



List No. 2. 



In order to perform experiments Nos. 34, 36, 46, 47, 48, 49, 51, 
65, 66, 80, 81, 113, the following additional apparatus is neces- 
sary: 



2 qt. Bunsen's Cells (10 p. c.) ... $2 20 

2 Platinum Plates, 1 x i^ inch (net) 40 
1 Charcoal Furnace, 18 in. (-^0 

p. c.) 2 50 

or 1 Charcoal Furnace, 24 
in. (20 p. c). $3.00, or 1 10- 
burner Gas Combustion Fur- 
nace (20 p. c), S20 00. 
1 25-in. hard Glass Tube, 1 in. 

bore (10 p. c.) 1 00 

or 1 25-in. Porcelain Combus- 
tion Tube, 1 in. bore (20 p. c), 
$1 75. 

3 pt. Woulff's Bottles, 2-necked 

(20 p. c.) 1 50 

1 hard Glass Tube, drawn out, 

12x1^ in. bore (net) 25 



1 Oxyhydrogen Blowpipe (20 

p. c.) S5 50 

2 Gasholders for Oxygen and 

Hydrogen, 5 gal. (20 p. c). . . 30 00 

1 Liebig's Condenser, 15 in. (20 

p.c.) 1 10 

2 Burettes, 50 c.c. xV (20 p. c.) 2 70 

2 Pinchcocks (20 p. c.) 30 

1 Copper Air-bath, 6x8 in. (20 

p. c.) 4 50 

1 Kellog-Bunsen's Vapor Lamp, 
complete (a substitute in case 
gas is not used as fuel) 
(net) 10 00 



$61 95 



THE ELEMENTS OF CHEMISTRY, 

CHAPTER I. 
CHEMICAL CHANGES— PHYSICAL CHANGES 

Some Familiar Changes. — You are all familiar with 
many changes which are taking place in the things around 
you. Take, for example, the changes which are called 
fire. You see substances destroyed by fire. They dis- 
appear. You feel the heat produced by the burning. 
You know that some things will burn and others will not. 
Again, you all know that iron when exposed to the air is 
changed, becoming covered with a reddish-brown sub- 
stance called rust. If fruit-juices or milk be allowed to 
stand in contact with the air they become sour. If a 
spark comes in contact with gunpowder there is a flash 
and the powder disappears, dense smoke appearing in its 
place. 

Changes of Another Kind. — If a piece of stone or of iron 
is brought in contact with something hot it becomes hot 
itself. If taken away it becomes cool again. If heated 
very hot it gives light. When, for example, iron becomes 
^' red-hot ^^ we can see it in a dark room. Iron may also 
be changed by contact with loadstone. After it has been 
rubbed with loadstone it has the power to attract and hold 



2 THE ELEMENTS OF CHEMISTRY. 

to itself other pieces of iron. When a solid body is struck 
with another solid a sound is produced. At a low tem- 
perature water is solid, forming ice. If the ice becomes 
warm enough it melts and becomes water. If the water 
is heated high enough it becomes steam. By cooling steam 
it changes to water, and by cooling water it changes to ice. 

Two Kinds of Change. — When a substance burns it 
becomes something entirely different. Iron-rust is not 
iron. Sour milk is not fresh milk. Gunpowder after the 
flash is not gunpowder. In these cases, then, the sub- 
stances that are changed disappear and something else is 
formed in their place. On the other hand, when a piece 
of iron that is hot is allowed to cool it is the same thing 
that it was before it was heated. Eed-hot iron soon ceases 
to give light if it is taken away from the fire. Water may 
be cooled down and changed to ice, and the ice heated and 
changed to water; and the water formed from the ice is 
exactly the same thing as the water from which the ice 
was formed. In these cases the substances are not per- 
manently changed. You see thus that we have two classes 
of changes presented to us for study: 

1st. Those which do not affect the composition 'of sub- 
stances. 

2d. Those which affect the composition of substances 
and give rise to the formation of new substances with new 
properties. 

Changes of the first kind are called physical changes. 
Those of the second kind are called chemical changes. 

Physics and Chemistry. — That branch of knowledge 
which has to deal with physical changes is known as 
physics; and that which has to deal with chemical changes 



CHEMICAL CHANGES— PHYSICAL CHANGES, 3 

is known as chemistry. Everything that has to do with 
motion, with heat, light, sound, electricity, and mag- 
netism, is studied under the head of Physics. Everything 
that has to do with the composition of substances and 
changes in the composition is studied under the head of 
Chemistry. 

All Physical and Chemical Changes are Related.- — 
Although at first sight the different kinds of change 
already mentioned appear to be quite distinct from one 
another, they are in reality closely related. If a body in 
motion is suddenly stopped it becomes hot. Many exam- 
ples of a similar change of motion into heat are familiar: 
a wire becomes hot when hammered on an anvil; a coin 
rubbed on cloth becomes hot. In both cases the cause of 
the heat is the interference with the motion. The hammer 
is stopped and becomes hot; the coin is not stopped, but 
the motion is interfered with, and we have to push harder 
in order to move it over the cloth than we should to move 
it in the air. Again, we know that by means of heat we 
can produce motion. The steam-engine is the best exam- 
ple of this. We build a fire; this heats the water in the 
boiler; the water is converted into steam, which expands 
and moves the piston, and the motion of the piston is the 
seat of all the complex motions that are found in the 
different parts of the engine. The train or ship moves. 
What moves it? Plainly, the heat is the cause of the 
motion. But we can go a step farther back and ask what 
causes the heat. The answer is clear. It is the burning 
of the fuel. But, in burning, the composition of the fuel 
is completely changed. When a piece of coal burns, then, 
its composition is changing, and as a result of this change 



4 THE ELEMENTS OF CHEMISTRY. 

heat is produced. The heat is, therefore, produced by a 
chemical change in the coal, and the motion of the steam- 
engine is the result of the chemical change taking place in 
the coal or wood which, in burning, produces the heat. 

Heat Causes Chemical Change. — Just as chemical change 
produces heat, as in the burning of a piece of wood, so 
heat causes chemical changes. 

Experiment l.—In a clean, dry test-tube put enough white 
sugar to make a layer J to | inch thick. Hold the tube in the 
flame of a spirit-lamp or a laboratory burner 
as shown in the figure, and heat until no more 
fumes are given off. What changes take 
place ? What do you notice on the sides of the 
tube ? What remains behind ? What is its 
color and taste ? Does it dissolve in water ? 
Is it sugar ? Is the change which has taken 
place chemical or physical ? What caused it ? 
Experiment 2. — From a piece of glass tubing 
of about ^ inch internal diameter cut off a 
piece about four inches long by making a mark 
across it with a triangular file, and then seiz- 
ing it with both hands, one on each side of the 
Fig- 1- mark, pulling and at the same time pressing 

slightly as if to break it. Clean and dry it, and hold one end in 
the flame of a laboratory burner until it melts together. During 
the melting twirl the tube constantly between the finger and 
thumb so that the heat may act uniformly upon it. After it has 
cooled down put into it enough red oxide of mercury (mercuric 
oxide) to form a layer i inch thick. Heat the tube as in the last 
experiment. — What change in color do you notice? What is 
deposited on the sides of the tube ? During the heating insert a 
splinter of wood with a spark on the end into the tube. What 
follows ? Take it out and put it back a few times. Is there any 
difference between the burning in the tube and out of it ? What 
difference ? How do you know that the red substance which you 
put into the tube has been changed ? Is the change chemical or 
physical ? What caused the change ? 




CHEMICAL CHANGES— PHYSICAL CHANGES. 



5 



Chemical Change Caused in Other Ways. — In the two 

experiments just performed heat caused chemical change. 
Chemical changes can be produced in other ways. The 
simplest way is by bringing substances together. 

Experiment 3. — Examine a piece of oalc-spar or marble. 
Notice whether it is hard or soft. Heat a small piece in a glass 
tube such as used in Experiment 2. Does it change in any way ? 
Does it dissolve in water ? In order to learn whether a substance 
is soluble in water proceed as follows : Put a piece about the size 
of a pea in a test-tube with distilled water. Thoroughly shake, 
and then, as heating usually aids solution, boil. Now pour off a 
few drops of the liquid on a piece of platinum-foil * or a watch- 
glass, and by gently heating cause the water to pass off as steam. 
If there is anything solid in solution there will be something 
solid left on the platinum-foil or watch-glass. If not, there will 
be nothing left. — Knowing now the general properties of the 
calc-spar or marble you will be able to determine whether it is 
changed or not. Treat a small 
piece with dilute hydrochloric 
acid. What takes place ? After 
the action has continued for 
about half a minute insert a 
lighted match in the upper part 
of the tube. Does the match 
continue to burn ? Does the sub- 
stance in the tube burn ? Is the 
invisible substance in the upper 
part of the tube ordinary air ? 
Why not ? Does the solid sub- 
stance disappear? In order to 
tell whether it has been changed 
chemically the hydrochloric acid 
must be got rid of. This can be done by boiling it, when it 
passes off in the form of vapor, just as water does, and then 
whatever is in solution will remain behind. For this purpose put 

* The expensive metal platinum is much used in chemical labora- 
tories, for the reason that it is not easily changed chemically by 
heat or by roost substajjceKS used in the laboratory, 




Fig. 2. 



6 THE ELEMENTS OF CHEMISTRY, 

the solution in a small, clean porcelain evaporating-dish, and put 
this on a vessel containing boiling water, or a water-bath. The 
operation should be carried on in a place where there is a good 
draught, so that the vapors will not collect in the working-room. 
They are not poisonous, but they are annoying. The arrange- 
ment for evaporating is illustrated in Fig. 2. After the liquid 
has evaporated and the substance in the evaporating-dish is dry, 
examine it and carefully compare its properties with those of the 
substance which was put into the test-tube. Is it the same sub- 
stance ? Is it hard or soft ? Does it change when heated in a 
tube ? Is there an appearance of bubbling when hydrochloric 
acid is poured on it ? Does it dissolve in water ? Does it change 
when allowed to lie in contact with the air ? 

Experiment 4. — Bring together in a test-tube a small piece of 
copper and some moderately dilute nitric acid. Hold the mouth 
of the tube away from your face and do not inhale the vapors. 
What is the appearance of the vapors given off ? What is the 
appearance of the liquid in the tube ? Does the copper dissolve ? 
Examine the solution, as in the preceding experiment, and see 
what has been formed. What are the properties of the sub- 
stance found after the liquid has evaporated ? Is it colored ? 
Is it hard or soft ? Does it change when heated in a tube ? Is it 
soluble in water ? Does it in any way suggest the copper with 
which you started ? 

Experiment 5.— Try the action of dilute sulphuric acid on a 
little zinc in a test-tube. An invisible gas will be given off. 
Hold the thumb loosely over the mouth of the tube, and after 
a few moments apply a lighted match to the mouth. What takes 
place ? After the zinc has disappeared evaporate the solution as 
before. Carefully compare the properties of the substance left 
behind with those of zinc. 

Experiment 6. — Hold the end of a piece of magnesium ribbon 
about eight inches long in a flame until it takes fire. Then hold 
the burning substance quietly over a piece of paper, so that the 
light, white substance which is formed may fall upon the paper. 
If the paper is dark the product can be seen more readily. 
Compare the properties of this product with those of mag- 
nesium. 

Experiment 7. — In a small dry flask of about four ounces 
capacity put a bit of granulated tin or of pur^^^tnrfoil. Pour 



CHEMICAL CHANGES— PHYSICAL CHANGES. 7 

upon it enough concentrated nitric acid to cover it. If no change 
takes place at first, heat gently, and presently you will have 
evidence that change is taking place. Is there anything in this 
experiment that suggests Experiment 4 ? What does the sub- 
stance that is left behind after the action is finished look like ? 
Compare the properties of the product with those of tin. 

Solution Aids Chemical Action. — In the cases just 

. studied it was only necessary to bring the substances 

together, when they acted at once. In each case one of 

the substances used was a liquid. Solids do not, as a rule, 

act upon one another as readily as liquids act upon solids. 

Experiment 8. — Mix together in a dry mortar a little dry 
tartaric acid and about an equal quantity of dry bicarbonate of 
soda (sodium bicarbonate). Do you see any evidence of action ? 
Now dissolve a little tartaric acid in water in a test-tube, and a 
little bicarbonate of soda in water in another test-tube. Pour 
the two solutions together. What evidence have you now that 
action takes place ? Pour water upon the dry mixture first made. 
Does action take place ? What causes the bubbling ? Will a 
match burn in the gas ? In which experiment already performed 
was a similar gas obtained ? 

Experiment 9. — Mix together in a dry mortar a little dry 
sulphate of iron (green vitriol) and a little dry ferricyanido of 
potassium (red prussiate of potash). Does action take place ? 
Make a dilute solution of each of the two substances and pour 
them together. What evidence have you that action takes place? 
Pour water on the dry mixture. Does action take place ? 

Summary. — From the experiments it will be seen (1) 

that heat causes chemical change; (2) that in some cases 

simple contact of substances is sufficient to cause chemical 

change; (3) that solution aids chemical change. In all 

the cases of chemical action thus far studied one thing was 

observed, viz., that the substances which were acted upon 

lost their own properties and new substances were formed. 

This is true in all cases of chemical action, and the truth 

may be statted thus: 



8 THE ELEMENTS OF CHEMISTRY, 

Whenever tivo or more suistances act upon one another 
chemically they lose their own properties^ and new sub- 
stances are formed with entirely different properties. 

Difference between Combining Chemically and simply 
Mixing. — By mixing is meant bringing things together 
closely, so that the particles of one shall be in contact 
with the particles of the other. We mix salt and sugar 
by putting them together in a vessel and shaking them, 
or by stirring as with a pestle in a mortar. The longer 
we stir the more closely the substances are brought 
together. But no matter how long we may stir the mix- 
ture, it remains a mixture and contains both sugar and 
salt. In some cases, by stirring, chemical action can be 
brought about, but generally not. 

Experiment 10. — Mix two or three grams of dry powdered 
roll-sulphur and an equal weight of very fine dry iron filings in a 
small dry mortar. Examine a little of the mixture with a micro- 
scope. Can you distinguish the particles of sulphur and those 
of iron ? Pass a small magnet over the mixture. Are particles 
of iron drawn out of the mixture ? Has chemical action taken 
place ? 

Experiment 11. — Caution! Garhon bisulphide oi- hisulpliide 
of carbon takes fire easily. In worMng with it Jceep away from 
flames. — Pour two or three cubic centimetres of bisulphide of 
carbon on a little powdered roll-sulphur in a dry test-tube. Does 
the sulphur dissolve ? Treat iron filings in the same way. Does 
the iron dissolve ? Now treat a small quantity of the mixture 
prepared in Experiment 10 with bisulphide of carbon. After the 
sulphur is dissolved pour off the solution in a good-sized watch- 
glass and let it stand. Examine what is left in the test-tube. 
Is it iron ? After the liquid has evaporated examine what is 
left on the watch-glass. Is it sulphur ? 

Experiment 12. — Mix three grams of finely powdered roll- 
sulphur and three grams of fine wrought-iron filings or powdered 
iron to be had of the druggists. Put the mixture in a dry test- 
tube. Heat gently at first and notice the changes, At first the 



CHEMICAL CHANGES— PHYSICAL CHANGES. 9 

sulphur melrs and becomes dark-colored. It may even take fire. 
But soon something else takes place. The whole mass begins to 
glow, and if you at once take the tube out of the flame the mass 
will continue to glow, becoming brighter. This will soon stop ; 
the mass will grow dark and gradually cool down. As soon as it 
reaches the ordinary temperature, break the tube and put the 
contents in a mortar. Does the mass look like the mixture of 
sulphur and iron with w^hich you started ? An examination with 
the microscope, the magnet, and bisulphide of carbon will prove 
that, while there may be a little iron left and possibly a little sul- 
phur, most of the bluish-black mass is neither iron nor sulphur, 
but a new substance with properties quite different from those of 
iron and sulphur. Treat a little of the substance with dilute 
sulphuric acid. Also treat a little of the mixture of iron and 
sulphur with dilute sulphuric acid. What difference do you 
observe between the two cases ? ^N'otice the odor. 

What has Become of the Iron and the Sulphur ? — In the 
last experiment a new substance was formed by the action 
of sulphur upon iron. Neither substance has been 
destroyed, but both have combined in a much more 
intimate way than when they were simply mixed together. 
This kind of combination which causes the characteristic 
properties of the combining substances to disappear is 
called chemical combination. Nothing is lost in the act, 
as can be shown by weighing the substances before and 
after action. 

Mechanical Mixtures and Chemical Compounds. — Bt a 
mixture the stibstances are itncliaiiged. They exist side hy 
side. In a chemical compound the substances which are in 
combination are completely changed. They are so intimately 
combined that they cannot be recognized by ordi^iary means. 

Compounds and Elements. — Most of the substances found 
in nature are made up of several others. Wood, for 
example, is very complex, containing a large number of 
distinct substances intimately mixed together. Some of 



lo THE ELEMENTS OF CHEMISTRY. 

these can be got out separately, but it is impossible to get 
tliem all out separately with the means at present at our 
command. Most of the rocks met with, and the different 
kinds of earth, as clay, sand, etc. , are also quite complex, 
and it is in most cases difficult to get out the substances 
contained in them. By proper methods, however, it is 
possible to decompose the complex substances found in 
nature so as to get simpler ones, and these again can 
usually be decomposed into still simpler ones which cannot 
be decomposed by any means known to us. Substances 
which we cannot decompose into simpler ones are called 
elements. Now, although there are thousands of different 
kinds of substances met with in nature, these are really 
made up of a comparatively small number of simple sub- 
stances or elements. The number of elements thus far 
discovered is between seventy and eighty, but the larger 
number of these are rare, and we might have an excellent 
knowledge of the essentials of chemistry without any 
knowledge of these rare elements. We shall find that 
most things we have to deal with are really made up of 
about a dozen elements, and that most of the chemical 
changes that are taking place around us, and that we need to 
study in order to get an insight into the nature of chemical 
action, take place between this small number of elements. 

An element is a substance that we cannot decompose into 
sifnpler snlstances. 

A compound is a substance that can be decomposed into 
simpler ones. A compound contaMs tioo or more elements 
held togetlier chemically. 

Examples of Elements and Compounds. — As examples of 
elements may be mentioned iron, copper, tin, silver. 



CHEMICAL CHANGES— PHYSICAL CHANGES, H 

gold, sulphur, and lead. As stated in the last paragraph, 
they are called elements for the reason that they cannot be 
decomposed into simpler substances. Among familiar 
compounds may be mentioned water, common salt or 
sodium chloride, blue vitriol or copper sulphate, chlorate 
of potash or potassium chlorate, marble or calcium car- 
bonate, sand or silicon dioxide. Each of these compounds 
consists of two or more elements held together in chemical 
combination. Water can be decomposed by yarious 
methods into two substances known as hydrogen and 
oxygen, and the sum of the weights of the hydrogen and 
oxygen obtained from a giyen weight of water is exactly 
equal to the weight of the water decomposed. Sodium 
chloride can be decomposed into the two elements sodium 
and chlorine, and the w^eight of the sodium added to the 
weight of the chlorine exactly equals the weight of the 
sodium chloride. On the other hand, the composition of an 
element cannot be changed without adding something to it. 

Chemical Action. — Just as the earth attracts all bodies 
to it in some mysterious way which we call grayitation, 
just as the magnet attracts pieces of iron, so substances 
are drawn together chemically and, if they come in con- 
tact under the proper conditions, cliemical action takes 
place. By this is meant that some change in composition 
is brought about ; that the substances which are brought 
together disappear and new ones make their appearance. 
But the quantity of matter remains the same. The ele- 
ments arrange themselyes differently. 

Three Kinds of Chemical Action. — The numerous cases 
of chemical action may be divided into three classes: (1) 
combination; (2) decomposition; and (3) double decomposi- 



12 THE ELEMENTS OF CHEMISTRY. 

Hon or metatliesis. As an example of combination the 

case of the action of iron on sulphur may be taken. The 

two elements combine directly, forming a compound 

known as iron sulphide. The action may bo represented 

thus : 

Iron + Sulphur — Iron Sulphide. 

A good example of decomposition is that of the action 

of heat on the red oxide of mercury or mercuric oxide (see 

Experiment 2). When this substance is heated two things 

are obtained from it: an invisible gas, oxygen, which 

passes out of the vessel and can be detected by the fact 

that substances burn in it more readily th. n they do in 

air; and a silvery-looking liquid, which is quicksilver or 

mercury. The action in this case may be represented 

thus: 

Mercuric Oxide = Mercury + Oxygen. 

In double decomposition two or more substances act 
upon one another and give rise to the formation of two or 
more new ones. Thus when hydrochloric acid acts upon 
marble (see Experiment 3) two substances, calcium chlo- 
ride and carbonic acid, are formed. This may be repre- 
sented thus : 
Hydrochloric Acid + Calcium Carbonate (or marble) = 
Calcium Chloride + Carbonic Acid. 

Most cases of chemical action which we have to deal 
with are of the third kind. 

The Cause of Chemical Action. — It is evident from what 
we have already learned that there is some power which 
can hold substances together in a very intimate way, so 
intimate that we cannot recognize them by ordinary 
means. We do not know what causes sulphur and iron to 



CHEMICAL CHANGES-PHYSICAL CHANGES. 13 

combine, but we know that they do combine. Similarly, 
we do not know what causes a stone thrown in the air to 
fall back again, but we know that it falls back. It is true 
we say that the cause of the falling of the stone is the 
attraction of gravitation, but this does not give us any 
information, for, if we ask what the attraction of gravita- 
tion is, we can only answer that it is that which causes all 
bodies to attract one another. So, too, we may say that 
the cause of the chemical union of substances is clieniical 
attraction. But in so doing we are only giving a name to 
something about which we know nothing except the 
effects which it produces. 

Importance of Chemical Action. — If this power, what- 
ever it may be, should cease to operate, what would be the 
result ? As far as we can see all substances known to be 
chemical cowponjids would be decomposed into the ele- 
ments of which they are composed, and there would be 
only about seventy or eighty different kinds of substances. 
All living things would cease to exist, and in their place 
we should have three invisible gases and something very 
much like charcoal. Mountains would crumble to pieces, 
and all water would disappear, giving two invisible gases. 
The processes of life in its many forms would be impossi- 
ble. These considerations will suffice to show the great 
importance of the subject of chemistry, and how impossi- 
ble it is without some knowledge of this subject to form 
any conception in regard to the most important phenomena 
of the universe. 

Occurrence of the Elements. — As has already been stated 
(p. 10), not more than a dozen elements enter largely into 
the composition of the earth. It has been estimated that 



14 THE ELEMENTS OF CHEMISTRY, 

the solid crust of the earth is made up approximately as 

represented in this table : 

Oxygen 47.29 per cent. 

Silicon 27.21 '' 

Aluminium 7.81 '* 

Iron 5.46 " 

Calcium 3.77 '' 

Magnesium 2.68 '' 

Sodium 2.36 '' 

Potassium 2.40 ' ' 

While oxygen forms a large proportion of the solid crust 
of the earth, it forms a still larger jDroportion (eight 
ninths) of water, and about one fifth of the air. Carbon 
is the principal element entering into the structure of 
living things, while hydrogen, oxygen, and nitrogen also 
are essential constituents of animals and plants. Nitrogen 
forms about four fifths of the air. 

The Names of the Elements. — The names of the ele- 
ments are formed in many different ways. The name 
chlorine is derived from a Greek word meaning greenish 
yellow, as this is the color of chlorine. Bromine comes 
from a Greek word meaning a stench, a prominent char- 
acteristic of bromine being its bad odor. Hydrogen is 
formed from two Greek words, one of which means water 
and the other to produce, signifying that it enters into the 
composition of water. Potassium is an element found in 
potash, and sodium is found in soda. 

The Symbols of the Elements. — It is convenient to use 
abbreviations for the names of the elements and com- 
pounds. Thus, instead of oxygen we may write simply 
0, for hydrogen H, for nitrogen N, etc. Frequently the 
first letter of the name of the element is used as the 
symbol. If the names of two or more elements begin with 



CHEMICAL CHANGES— PHYSICAL CHANGES. 



15 



the same letter, this letter is used, but some other letter 
of the name is added. Thus, B is the symbol of boron, 
Ba of barium, Bi of bismuth, etc. In some cases the 
symbols are derived from the Latin names of the elements. 
Thus, the symbol of iron is Fe, from ferrxim; of copper, 
Cu, from cuprum; of mercury, Hg, from hydrargijriim.^ 
etc. The symbols of the more common elements will soon 
become familiar by use. It is not desirable to attempt to 
commit them to memory at this stage. 

List of the Elements and their Symbols. — In the table 
here given the names of those elements which are most 
widely distributed, and which form by far the largest part 
of the earth, are printed in small capitals. The names 
of those which are very rare are printed in italics. 



Aluminium Al 

Antimony Sb 

Argon A 

Arsenic As 

Barium Ba 

Bismuth Bi 

Boron B 

Bromine Br 

Cadmium Cd 

CcBsium Cs 

Calcium Ca 

Carbon C 

Cerium Ce 

Chlorine CI 

Chromium Cr 

Cobalt Co 

Columbium Cb 

Copper Cu 

Erbium Er 

Fluorine F 

Gadolinum Gd 

Gallium Ga 

Germanium Ge 

Glucinum Gl 

Gold Au 

Helium He 



Hydrogen H 

Indium In 

Iodine I 

Iridium Ir 

Iron Fe 

Krypton Kr 

Lanthanum La 

Lead Pb 

Lithium Li 

Magnesium Mg 

Manganese Mn 

Mercury Hg 

Molybdenum Mo 

Neodymium Nd 

Neon Ne 

ISTickel M 

Nitrogen N 

Osmium Os 

Oxygen O 

Palladium Pd 

Phosphorus P 

Platinum Pt 

Potassium K 

Praseodymium . . . . Pr 

Rhodium Rh 

Rubidium Rb 



Ruthenium Ru 

Samarium Sm 

Scandium Sc 

Selenium Se 

Silicon Si 

Silver Ag 

Sodium Na 

Strontium Sr 

Sulphur S 

Tantalum Ta 

Tellurium Te 

Thalliuin Tl 

Thorium ..Th 

Thulium Tu 

Tin Sn 

Titanium Ti 

Tungsten W 

Uranium U 

Vanadium V 

Xenon X 

Ytterbium Yb 

Yttrium Y 

Zinc Zn 

Zirconium Zr 



i6 THE ELEMENTS OF CHEMISTRY, 

What We Shall Study. — In the course which you have 
begun you will study only the most common elements and 
their action upon one another. In this way you will be 
able to learn much about the chemistry of many interest- 
ing things, such as burning, the rusting of iron, the 
growth of plants and animals, the extraction of useful 
metals from their ores, the manufacture of illuminating- 
gas, of soap, etc., etc., and at the same time you will 
acquire a knowledge of the general principles of chemistry 
which will enable you to take a more intelligent view of 
the universe than you can without this knowledge. 



CHAPTEK IL 

THE CHEMISTRY OF THE AIR. 

The Air Causes Chemical Changes. — One of the most 
interesting, most common, and most important chemical 
changes with which we are familiar is that which is known 
as burning. Xo matter how we may begin the study of 
the chemistry of the things around us, we are at once 
brought face to face with the fact that the air takes part 
in chemical change. 

Experiment 13. — In a small porcelain crucible arranged as 
shown in Fig. 3 put a small piece of lead. Heat by means of a 
laboratory burner, and notice the changes that take place. 
After the lead is melted stir the substance 
with a thick iron wire while heating. Con- 
tinue to heat and stir until the substance is no 
longer liquid. What is its appearance now ? 
Let it cool. Is it lead ? What difference is 
there between the action in this case and in 
the case of melting ice and cooling the water 
down again ? Which is chemical action and 
which physical action ? Why ? ^^^- ^• 

Experiment 14. — Heat a piece of zinc in the same way as you 
have just heated lead. What changes take place ? 

ExPERLMENT 15. — Heat a piece of tin in the same way. What 
changes take place ? 

What Caused the Changes? — By heating lead, zinc, and 

tin in the air, then, they are changed, to powders which 

^7 




1 8 THE ELEMENTS OF CHEMISTRY, 

do not melt. The question will suggest itself, does the 
heat alone cause these changes or has the air something to 
do with them ? The air alone plainly does not cause the 
changes, for they do not take place until the substances 
are heated. To learn whether the air has anything to do 
with them we shall have to heat the substances in such a 
way as to keep the air from getting at them. This can 
be done by putting in the vessel something which melts 
and which will float on the melted metal. Such a sub- 
stance is ordinary borax. 

Experiment 16. — Repeat Experiments 13, 14, and 15, adding 
in each case enough borax to form a complete cover to the metal 
after both are melted. Do the metals melt? Are they changed 
to powders as in the previous experiments ? 

Many Similar Pacts are Known. — The examples given 
above are only a few of a large number of similar ones 
known. Hence the statement that many metals when 
heated in the air undergo chemical change and are con- 
verted into powders which do not melt. The powders are 
formed by the action of the air on the heated metals, for 
if the air is kept away from the metals the changes do not 
take place. 

The Metals Increase in Weight when Heated in the 
Air. — If you were to weigh the metals used in Experiments 
13, 14, and 15 and then weigh the powders obtained, you 
would find that in each case the powder weighs more than 
the metal. This fact taken together with the others 
already learned shows that there is something in the air 
which at high temperatures combines with the metals tin, 
zinc, and lead. 

Burning in the Air. — The phenomenon of burning takes 
place in the air, and the question suggests itself, has the 



THE CHEMISTRY OF THE AIR. 



19 



air anything to do with the burning ? Yon know that if 
you shut up a stove completely the fire dies down, and 
unless the draught-door is opened the fire goes out. If 
you want the fire to burn more actively you open the 
draught-door, when air is drawn in and the burning is 
made to take place more rapidly. A fire burns better 
when air is blown into it Avith a bellows. A candle is put 
out when an)rthing is brought down upon the flame in 
such a way as to keep out the air. When a smouldering 
fire is covered with ashes it goes out. All these facts, 
Avhich are well known to every one, make it appear prob- 
able that the air has something to do with burning, but 
they do not show what. In order to learn this we shall 
have to experiment carefully, noticing everything that 
takes place. 

Experiment 17. — Fix a short bit of candle on a large flat cork 
or a block of wood. Light the candle and place it with the block 
on the surface of water contained in a pail or some other appro- 
priate vessel. Place over it a good-sized glass vessel, either a 
wide-mouthed bottle or a good-sized fruit-jar, as represented in 
Fig. 4, so that the candle and cork are in the glass vessel and the 
mouth of the vessel is beneath the 
surface of the water. Hold it in this 
position for a few minutes and ob- 
serve what takes place. Does the 
candle continue to burn ? Is all the 
air contained in the vessel used up 
when the candle goes out ? Try the 
experiment a second time, and when 
the flame is nearly extinguished raise 
the glass vessel so that air can get 
in. Does this make any difference ? 
do these experiments prove ? 

A Candle Will Not Burn in the Air that is Left. — If, 

after the candle has gone out, you place your hand or a 




Fig. 4. 

What difference ? 



What 



THE ELEMENTS OF CHEMISTRY. 



ground- glass plate over the mouth of the vessel and turn 
it mouth upward, and then insert into it a lighted candle 
on a wire, the candle will be extinguished. You see that 
the air which is left in the vessel after a candle has burned 
in it and gone out is not the same as ordinary air. 

Experiment 18. — Try the experiment just mentioned. The 
candle on the wire should be arranged as shown in Fig. 5. 

Does the Candle Increase in Weight ? 

— You know that in burning the candle 
gradually disappears, and from this you 
would be inclined to think that it is 
destroyed. But if you were to collect 
the smoke which is given off and weigh 
it, you would find that it weighs more 
than that part of the candle which has 
burned up. So that instead of there being 
a loss of matter there is apparently a gain. 

Experiment 19. — On one pan of an appropriate balance place 
a candle, and directly over it suspend a wide glass tube contain- 
ing pieces of caustic soda, a substance which has the power to 
absorb most of the smoke given off from the burning candle. 
Place a similar glass tube with caustic soda on the other pan of 
the balance and exactly balance the two pans. Now light the 
candle, and in the course of a few minutes the pan with the 
candle on it will sink, showing that it is heavier than the other. 

One Fifth of the Air is Used up when Anything Burns 
in a Closed Vessel. — By careful experiments which it 
would be difficult to repeat here it has been shown that 
only one fifth of the air is capable of keeping up the 
process of burning, while the rest is an inactive substance 
in which burning cannot take place. If, for example, you 
could heat a piec§ qI l^ad or zinc in a closed vessel for a 




Fig. 5. 



THE CHEMISTRY OF THE AIR. 



21 




time, then let it cool and open the vessel under water, you 
would find that water would t\ 

rush in and fill about one fifth 
of the vessel, showing that 
this much air had been used 
up. If you should weigh the 
metal before and after heat- 
ing you would find that it had 
increased in weight, and if 
you should weigh the air used 
up you would find that its 
weight was exactly equal to the fig. e. 

increase of weight of the metal. A great many experi- 
ments of this kind have been performed, and they have 
shown that when a sitlstance liirns it takes up sometMng 
from the air and increases in weight exactly as much as 
the air loses. 

The Air Consists Mainly of Two Substances. — The air 
then consists of two substances^ only one of which can 
keep up the process of burning. This one is known as 
oxygen. The other, in which things cannot burn, is 
known as nitrogen. Besides these the air always contains 
smaller quantities of other substances, particularly water 
vapor., carbonic acid (or carbon dioxide), ammonia., argon., 
etc. We shall soon study these substances and learn 
something about the part they play in the air. Oxygen 
and nitrogen are called elements because no one has been 
able to decompose them and get anything simpler from 
them. 



CHAPTER III. 
OXYGEN 

Occurrence of Oxygen. — Oxygen is the most widely dis- 
tributed element, and it occurs also in yery large quantity. 
It has been stated that it forms between forty and fifty per 
cent of the solid crust of the earth, eight ninths of water 
and one fifth of the air by bulk. 

Preparation of Oxygen. — We have oxygen around us in 
great abundance in the air, but it is mixed with nitrogen, 
and it is difficult to separate the two so as to get the 
oxygen. The easiest way to get oxygen is by heating 
certain substances that contain it. One of the simplest 
examples of this kind is the oxide of mercury. When this 
is heated it gives mercury and oxygen. When mercury 
itself is heated in the air for some time to near its boiling 
point it is gradually changed to a red powder, just as lead 
and tin and zinc are changed to powders when heated in 
the air. This powder is a compound of mercury and 
oxygen. When the compound is heated to a high tem- 
perature it is decomposed into its elements, mercury and 
oxygen. 

Collection of Oxygen. — The oxygen given off from the 
oxide of mercury is most conveniently collected by causing 
it to displace water. For this i3urpose the apparatus 
should be arranged as represented in Fig. 7, On heating 

22 



OXYGEN. 23 

the oxide, the oxygen which is set free necessarily passes 
through the narrow tube and escapes beneath the mouth 
of the inverted glass vessel which is filled with water. 
The gas, being lighter than water and not very soluble in 
it, rises and the water is displaced. The oxide of mercury 




Fig. 7. 

should be heated in a tube made of hard glass closed at 
one end. 

Oxygen Made from Potassium Chlorate. — Another sub- 
stance which readily gives up oxygen when heated is 
potassium chlorate or, as it is commonly called, chlorate 
of potash. This is manufactured in large quantities and 
is easily obtained. It contains the three elements potas- 
sium, chlorine, and oxygen. When heated it, gives up the 
oxygen, and a compound of potassium and chlorine, 
known as potassium chloride, very much like common 
salt, is left behind. 

Experiment 20. — Arrange an apparatus as shown in Fig. 8. 
A represents a retort of about 100 c.c. capacity. jB is a piece of 
rubber tubing which is in turn connected with a piece of glass 
tubing bent upward at the end. This end is placed under the sur- 
face of the water in C In A put 2 or 3 grams (about a sixteenth 
of an ounce) of potassium chlorate, and gently heat by means of the 
burner. Notice carefully what takes place. When gas comes oif 



24 



THE ELEMENTS OF CHEMISTRY. 



freely bring the inverted cylinder E filled with water over the 
end D of the tube, and let the bubbles of gas rise in the cylinder. 
Examine the gas by placing a glass plate over the mouth of the 
vessel containing it and inverting it. Insert into it a stick with 




Fig. 8. 

a spark on its end. What takes place ? Is the gas contained in 
the vessel ordinary air ? 

Oxygen Made by Heating a Mixture of Potassium 
Chlorate and Manganese Dioxide. — The most conyenient 
way to make oxygen in the laboratory is to lieat a mixture 
of equal parts of potassium chlorate and manganese 
dioxide or ^^ black oxide of manganese/^ This mixture 
gives off oxygen readily when heated. The potassium chlo- 
rate alone is decomposed under these circumstances, the 
manganese dioxide remaining unchanged. It is not defi- 
nitely known how the manganese dioxide helps the action. 

Experiment 21.— Mix about 10 grams (or about a quarter of an 
ounce) of potassium chlorate with an equal weight of coarsely 
powdered manganese dioxide in a mortar. Heat the mixture * in 

* Black oxide of manganese is sometimes adulterated with other 
substances, and w^hen heated with potassium chlorate it may then 
give rise to explosions. It should be tested before using by mixing 
a very small quantity with potassium chlorate and heating in a test- 
tube. If the decomposition takes place quietly the substance may 
be used for the preparation of oxygen. 



OXYGEN. 25 

a glass retort arranged as shown in Fig. 8 and collect the gas by 
displacement of water in appropriate vessels — cylinders, bell- 
glasses bottles with wide mouths, etc. 

Physical Properties of Oxygen. — Having thus learned 
how to get oxygen, you may proceed to study its proper- 
ties. In the first place, the gas is invisible. The slight 
cloud that appears in the vessels when the gas is first col- 
lected is due to the presence of a very small quantity of a 
substance that is not oxygen. If the vessels are allowed 
to stand for a few minutes the cloud will disappear, and 
the vessels will look as if they were filled with air. The 
gas is tasteless and inodorous. [Inhale a little from one 
of the small bottles.] It is slightly heavier than the air. 
When subjected to an extremely high pressure and low 
temperature it is converted into a blue liquid. The 
properties of oxygen to which reference has thus far been 
made are its physical properties. These are its appear- 
ance, taste, smell, relative weight, and changes in its 
condition which still leave it in the elementary form or 
uncombined chemically. 

Chemical Conduct of Oxygen. — In order to get an idea 
of the way in which oxygen acts upon some simple sub- 
stances under ordinary circumstances a few experiments 
should be performed. We want to learn: What changes 
oxygen can efEect in other substances; what conditions are 
necessary in order that it may act chemically; what 
products are formed, etc., etc. 

The Action of Oxygen at the Ordinary Temperature. 

Experiment 22. — Turn three of the bottles containing oxygen 
with the mouth upward, leaving them covered with glass plates. 
Into one introduce a little sulpliur in a so-called deflagrating- 
spoon, — a small cup of iron or brass attached to a stout wire that 



26 THE ELEMENTS OE CHEMISTRY, 

passes through a round metal plate, usually of tin (see Fig. 9). 
In another put a little charcoal (carbon), and in a third a piece of 
phosphorus ^ about the size of a pea. Let them stand quietly and 
notice what changes, if any, take place. 

What these Experiments Show. — These experiments 
show that oxygen does not act upon sulphur and carbon 
when brought in contact with them at the ordinary tem- 
perature, and that the action upon phosphorus is slight. 
We might perform experiments of this kind with a great 
many substances, and we should reach the conclusion that 
at the ordinary temperature oxygen does not readily act 
upon substances. Indeed, as the air contains a consider- 
able proportion of oxygen, it is clear that oxygen does not 
readily act upon substances at ordinary temperatures or 
action would constantly be taking place between the air 
and many of the substances exposed to it. 

Slow Action of Oxygen at the Ordinary Temperature. — 
Upon some substances oxygen does act even at ordinary 
temperature. Some metals, as iron, become covered with 
a layer of rust when exposed to the air. This is due 
partly, at least, to the action of the oxygen of the air. 
Wood and other vegetable substances undergo slow decom- 
position when exposed to the air, in consequence of the 
action of the oxygen. Animal substances undergo decom- 
position comparatively readily when exposed to the air. 
The process of decay is partly due to the action of oxygen 
at the ordinary temperature. 

* Phosphorus should be handled with great care. It is kept 
under water, usually in the form of sticks. If a small piece is 
wanted, take out a stick with a pair of forceps, and put it under 
water in an evaporating-dish. While it is under the water cut off a 
piece of the size wanted. Take this out by means of a pair of 
forceps, lay it for a moment on a piece of filter-paper, which will 
absorb most of the water, then quickly put it in a spoon. 



OXYGEN, 



27 



The Action of Oxygen in Animal Bodies. — The most 
important illustration of the action of oxygen at low tem- 
peratures is that which takes place in our bodies and the 
bodies of all animals. The food that we partake of under- 
goes many changes; some of the substances uniting with 
oxygen. Then, too, we take large quantities of oxygen 
into our lungs in ireathijig. This acts upon various sub- 
stances that are presented to it in the lungs; it combines 
with them, forming other substances that can easily be 
got rid of. More will be said in regard to the breathing 
of animals and plants when the subject of carbon and its 
compounds with oxygen is taken up. 

The Action of Oxygen upon Heated Substances. — Sup- 
pose that before putting them in the oxygen we heat the 
substances in Experiment 22, what will then take place ? 

Experiment 23. — In a deflagrating-spoon set fire to a little sul- 
phur and let it burn in the air, Notice whether it burns with 
ease or with difficulty. Notice the odor of the fumes which are 
given off. Now set fire to another small portion ^nd introduce it 
in a spoon into one' of the vessels containing oxygen, as shown in 
Fig. 8. Does the sulphur burn more 
readily in the oxygen or in the air ? 
Notice the odor of the fumes given off. 
Is it the same as that noticed when the 
burning takes place in the air ? 

Experiment 24. — Perform similar 
experiments with charcoal. 

Experiment 25. — Burn a small piece 
of phosphorus in the air and in oxygen. 
In the latter case the light emitted 
from the burning phosphorus is so Fia. 9. 

intense that it is painful to some eyes to look at it. After the 
burning is over let the vessel stand. Does it become clear ? 

What Took Place in these Experiments? — In the first 

place, the substances were simply heated before they were 




28 THE ELEMENTS OF CHEMISTRY. 

introduced into the oxygen. Nothing was added to them. 
It is clear, therefore, that while oxygen does not act upon 
these substances at the ordinary temperature, it does act 
upon them at higher temperatures. But what does the 
action consist in ? We can determine this only by a care- 
ful study of the substances before and after the action. 
We must know not only what substances are brought 
together, hut also luliat the weight of each is; and we must 
know what substances are left behind, and the exact weight 
of these. By means of accurate experiments it has been 
shown repeatedly that the substances which burn in 
oxygen disappear as such, and that in each case a definite 
quantity of oxygen is also taken up. The result of the 
experiments can be stated thus : The weight of the siiistance 
turned plus the lueight of the oxygen taken up is exactly 
equal to the weight of the product formed. 

Burning is Combining with Oxygen. — From what we 
have learned we may conclude that when a substance burns 
in oxygen the act consists in the chemical combination of 
the two. 

Burning in the Air. — To determine whether burning in 
the air is the same act as burning in oxygen it is necessary 
to burn the same things in air and in pure oxygen and see 
whether the products are the same. This has been done 
a great many times, and always with the same result. 
Whether a substance burns in the air or in pure oxygen 
the same product is formed, and nothing else. It is 
therefore certain that the act of burning in the air is due 
to the presence of oxygen. As we have already seen, there 
is another substance present in the air in large quantity. 



OXYGEN. 29 

and it is due to this fact that burning does not take place 
as readily in the air as in oxygen. 

Combustion. — By the term combustion in its broadest 
sense is meant any chemical act that is accompanied by 
an evolution of light and heat. Ordinarily, however, it 
means the union of substances with oxygen as this union 
takes place in the air, with evolution of light and heat. 
Substances that have the power to unite with oxygen are 
said to be co7nbiistihle, and substances that have not this 
power are said to be incomiustiUe. Most of the elements 
combine with oxygen under proper conditions, and are 
therefore combustible. Most compounds formed by the 
union of oxygen with combustible substances are incom- 
bustible. They contain oxygen and they cannot directly 
combine with any more. 

Some Substances that do not Burn in the Air Burn in 
Oxygen. — The best illustration of this fact is that of iron. 
This metal, as you know, does not burn in the air under 
ordinary circumstances. If it did, all our stoves, iron 
vessels, and iron buildings would burn up. In pure 
oxygen, however, iron burns readily. 

Experiment 26. — Straighten a steel watch-spring * and fasten 
it in a piece of metal, such as is used for fixing a deflagrating- 
spoou in an upright position ; wind a little thread around the 
lower end, and dip it in melted sulphur. Set fire to this and 
insert it into a vessel containing oxygen. For a moment the sul- 
phur will burn as in Experiment 23; but soon the steel will begin 
to burn brilliantly, and the burning will continue as long as there 
is oxygen left in the vessel. The phenomenon is of great beauty, 

* Old watch-springs can generally be had of any watch maker or 
mender for the asking. A spring can be straightened by unrolling 
it, attaching a weight, and suspending the weight by the spring. 
The spring is then heated to redness from one end to the other by 
means of a Bunsen burner. 



30 THE ELEMENTS OF CHEMISTRY. 

especially if observed in a dark room. The walls of the vessel 
become covered with a dark reddish-brown substance, some of 
which will also be found at the bottom in large pieces. — Instead 
of the watch-spring iron picture- wire may be used. It is only 
necessary to heat the end and dip it into powdered sulphur before 
putting it into the vessel containing the oxygen. 

Kindling Temperature. — You have seen that substances 
do not usually combine with oxygen at ordinary tempera- 
tures, but that in order to effect the union the tempera- 
ture must be raised. If this were not the case it is plain 
that every combustible substance in nature w^ould burn 
up, for the air supplies a sufficient quantity of oxygen for 
this purpose. Some substances need to be heated to a 
high temperature before they will combine with oxygen; 
others require to be heated only slightly. Every combus- 
tible substance has its kindling temperature — that is, the 
temperature at w^hich it will unite with oxygen. Below 
this temperature it will not unite with oxygen. Watch a 
stick of w^ood burning, and observe how, as we say, ^^the 
fire creeps ^^ along it. The reason of the slow advance is 
simply this : only those parts of the stick which are nearest 
the burning part become heated to the kindling tempera- 
ture. They take fire and heat the parts nearest them, and 
so on gradually throughout the length of the stick. 

Heat a Result of Combustion. — We know that whenever 
a thing burns it gives out heat, and generally light. The 
heat is a result of the act of chemical combination, and 
the light is due to the heat. In general, whenever chemical 
combination takes i)lace heat is given off. This is probably 
due to the rapid coming together of the particles of the 
substances that combine, just as a bullet is heated by being 
rapidly projected against a hard target that stops it. 



ox Y GEN. it 

Chemical Energy and Chemical Work. — Any substance 
that has the power to combine with others can do chemical 
work; it possesses chemical energy. Thus all combustible 
substances can do work. In combining with oxygen heat 
is given off, and this can be changed into motion. To go 
back to the example of the steam-engine, that was referred 
to in Chapter I, the cause of the motion is the burning 
of the fuel. 

Products of Combustion. — The substances formed in 
combustion are in general known as oxides. The com- 
pound of zinc and oxygen is called zinc oxide; that of 
silver and oxygen, silver oxide^ etc. . 



CHAPTEE IV. 
COMBINING WEIGHTS 

Elements Combine in Definite Weight. — A certain 

weight of tin always combines with a definite weight of 
oxygen. If equal weights of sulphur and iron are mixed 
and caused to act chemically by the aid of heat, it will be 
found that some of the sulphur is left over in the uncom- 
bined state after the action is over. If we should take 
twice as much iron as sulphur, then, after the action, 
some iron would be left over. An extensive examination 
has shown conclusively that each chemical compound 
always contains the same elements in exactly the same pro- 
portions. The compound of sulphur and iron always 
contains exactly 36.41 per cent of sulphur and 63.59 per 
cent of iron. The compound of tin and oxygen always 
contains exactly 78.74 per cent of tin and 21.26 per cent 
of oxygen, and so on throughout the list of chemical 
elements. 

The Law of Definite Proportions. — These facts were dis- 
covered by the united efforts of a large number of chemists 
continued through many years. They are of great im- 
portance. They are summed up in the general statement : 

Chemical comhination ahvays takes place lehveen definite 
weights of suhstances. 

This is known as the law of definite proportions. 

32 



COMBINING IVEIGHTS. 33 

What a Natural Law is. — A natural law is simply a 
statement of. what we have every reason to believe to be 
the truth. Every fact known to us in regard to chemical 
combination is in accordance with the law of definite pro- 
portions. It expresses what has been learned by a study 
of chemical facts. This law, as well as other natural 
laws, can never be proved to be absolutely true, for the 
reason that we cannot examine every case to which the law 
applies. But if, after examining a very large number of 
cases, we find that the law holds true in them, we may 
conclude that it is true of all cases. When we say that all 
bodies attract one another, do we know this to be abso- 
lutely true ? Certainly not. But we do know that so far 
as those bodies are concerned which come under our 
observation the statement is true, and therefore we have 
reason to believe that it is true of all bodies. 

Proportions by Weight in which the Elements Combine. 
— A careful study of the figures representing the compo- 
sition of chemical compounds reveals a remarkable fact 
regarding the relative quantities of one and the same 
element which enter into combination with other elements. 
The proportions by weight in which some of the elements 
combine chemically are stated in the following table : 



Sulphur 1 ; 
Oxygen 1. 


Iron 7; 
Oxygen 2. 


Iron 7; 
Sulphur 4. 


Magnesium 3; 
Oxygen 2. 


Tin 59; 

Oxygen 16. 


Zinc 65; 
Oxygen 16. 


Tin 59; 
Sulphur 16. 


Zinc 65; 
Sulphur 32. 


Sodium 23; 
Oxygen 8. 


Sodium 23; 
Sulphur 16. 


Potassium 39; 

Oxygen 8. 


Potassium 39; 
Sulphur 16. 



34 THE ELEMENTS OF CHEMISTRY, 

You see that for iron, tin, zinc, sodium, and potassium the 
same figures are used, whether you have the compounds 
of these elements with oxygen or with sulphur. Now, 
if we were to determine the composition of all compounds 
which contain zinc, we should find that the relative weight 
of zinc present could, in nearly all cases, be expressed 
by the number 65. Similarly the quantity of sodium 
in sodium compounds could be expressed by the number 
23, and that of potassium in potassium compounds by 39. 

Combining Weights of the Elements. — For every ele- 
ment a certain number can be selected, such that the 
proportions by weight in which this element enters into 
combination with others can be expressed by the number 
or by a simple multiple of it. These numbers are called 
the comiining lueights. It is not by any means an easy 
matter to determine which numbers are most convenient 
for all cases; and if the selection is to be determined solely 
by convenience, there may be difEerences of opinion as to 
what is most convenient. We shall see a little later that 
while the numbers primarily express the combining 
weights and nothing else, and are based solely upon 
determinations of the composition of chemical compounds, 
they have come to have a deeper meaning, and are now 
determined by methods that cannot easily be explained at 
this stage. The facts which it is important that you 
should understand now are : 

(1) That chemical action takes place between definite 
weights of substances; and 

(2) That the relative weights of the elements which 
enter into combination with one another can be expressed 
by numbers called the combining weights. 



COMBINING IVEIGHTS, 35 

Symbols of Chemical Compounds. — Yon have learned 
that the chemist uses a kind of short-hand to express the 
names of the elements. Instead of the name oxygen he 
writes the symbol 0^ etc. Now these symbols stand not 
only for the names but also for the combining weights of 
the elements. Thus, stands not only for the name 
oxygen but for 16 parts by weight; Fe stands for 56 parts 
by weight of iron, etc. To express a compound in the 
short-hand, the symbols of the elements contained in it 
are simply placed side by side. Thus, common salt or 
sodium chloride consists of the elements sodium and chlo- 
rine, which are combined in the proportion of their com- 
bining weights. The symbol of the compound is IS'aCl, 
which means a compound of the elements sodium and 
chlorine in the proportion 23 parts by weight of sodium 
and 35.5 of chlorine. 

What is Meant by " Parts by Weight."— When we say 
that '' stands not only for the name oxygen but for 16 
parts by weight '^ we have in mind an imaginary standard. 
What really stands for is 16 times the weight of matter 
represented by H which stands for 1 part by weight of 
hydrogen. The reason why hydrogen is selected as the 
standard of comparison will be pointed out later. 

How Chemists Express Chemical Reactions. — The sym- 
bols are of great conyenience when it is desired to express 
what has taken place in a chemical reaction. Thus you 
have seen that when the compound mercury oxide, HgO, 
is heated, it is decomposed into mercury and oxygen, a 
fact which is clearly expressed by the equation 

HgO = Hg + 0, 

■which tells not only the fact that decomposition takes 



3^ THE ELEMENTS OF CHEMISTRY. 

place but the proportions by weight in which the sub- 
stances take part. Thus, the compound, HgO, contains 
the elements in the proportion of 200 parts by weight of 
mercury to 16 of oxygen. When 216 parts by weight of 
this compound are decomposed 200 parts by weight of 
mercury and 16 of oxygen are obtained. As in chemical 
reactions matter is neither destroyed nor created, the same 
weight of matter must be represented on each side of the 
equation, or ^^the equation must balance.-'^ 

A Chemical Problem. — Suppose you wish to know how 
much oxygen is contained in 50 grams of mercury oxide, 
how could you determine it ? You know that in 216 parts 
by weight of the compound there are 16 parts by weight 
of oxygen; or, that in 216 grams of the compound there 
are 16 grams of oxygen. How many grams of oxygen are 
there in 50 grams of the compound ? Plainly the answer 
is given by solving the expression 

216 : 50 :: 16 : the number of grams of oxygen contained 
in 50 grams of the oxide. 

Or -^y^-g of mercuric oxide being oxygen, how much oxygen 
is there is 50 grams of the oxide ? Plainly ^y^ x 50 = 
3-|f grams. 

Law of Multiple Proportions. — Two elements frequently 
combine in more than one set of proportions. Thus, 
while ordinarily iron and sulphur combine in the propor- 
tion 56 of iron to 32 of sulphur, they also combine in the 
proportion 56 of iron to 64 of sulphur. Tin combines 
with oxygen in two proportions, forming two distinct com- 
pounds. In one 118 parts of tin are combined with 16 
parts of oxygen; in the other 118 parts of tin are combined 
with 32 parts of oxygen. The elements potassium, chlo- 



COMBINING IVEIGHTS. 37 

rine, and oxygen combine in several proportions as repre- 
sented here: 

Potassium 39 39 39 39 

Chlorine 35.5 35.5 35.5 35.5 

Oxygen 16 32 48 64 

It Avill be observed that while in the compounds 
mentioned the quantities of oxygen and sulphur united 
with the same element or elements vary^ these quantities 
are closely related to one another. In the case of iron and 
sulphur there is twice as much sulphur, relatively;, in one 
compound as in the other. So, also, in the compounds of 
tin and oxygen there is twice as much oxygen combined 
with a given quantity of tin in one case as in the other. 
Finally, in the four compounds which are made up of 
potassium, chlorine, and oxygen the quantity of oxygen 
varies, being twice as great in the second compound as in 
the first, three times as great in the third, and four times 
as great in the fourth. These facts, and others of the 
same kind, are summed up in the Laio of Midtiple Pro- 
portions, which may be stated thus : 

If hvo elements^ A and B, comline in different propor- 
tions, the relative quantities of B ivliicli comline ivith any 
fixed quantity of A lear a simple ratio to one another. 

The case of the compounds of potassium, chlorine, and 
oxygen does not come exactly under this law, as they do 
not consist of two elements. It will be observed, however, 
that these compounds illustrate the same principle. The 
relative weights of the potassium and chlorine do not 
change, while the weights of oxygen combined with fixed 
quantities of the other two elements bear a simple ratio to 
one another. 



SS THE ELEMENTS OF CHEMISTRY. 

Symbols of Compounds of Elements Combined in More 
than One Proportion. — As has already been stated, when 
two elements combine in the simplest proportion the 
symbol of the compound is made by putting the symbols 
of the elements side by side, as in HgO, XaCl, etc., etc. 
If it is desired to represent compounds of the same ele- 
ments combined in different proportions, use is made of 
small figures placed below the line, as in the symbols 
SO,, CO2, H2S0^, etc., etc. The meaning of the figures 
is this: In the compound SO^ sulphur and oxygen are 
combined in the proportion of the combining weight (32) 
of sulphur and twice the combining weight (16) of oxygen, 
or 32 parts by weight of suljDhur to 32 parts by weight of 
oxygen, which happens to be the same as 1 part by weight 
of one to 1 part by weight of the other. The symbol 
H^SO^ represents a compound made up of hydrogen, sul- 
phur, and oxygen in the proportion ttvice the combining 
weight of hydrogen (1), the combining weight of sulphur 
(32), and f 0117' times the combining weight of oxygen (16); 
or 2 parts by weight hydrogen, 32 parts by weight sulphur, 
and 64 parts by weight oxygen, making all together 98 
parts by weight of the compound. 

Problem. — How much sulphur is there in 60 grams of the com- 
pound H2SO4 (sulphuric acid) ? How much oxygen ? How much 
hydrogen ? 



CHAPTEK V. 
NITROGEN 

Occurrence of Nitrogen. — You have already learned that 
about four fifths of the bulk of the air is nitrogen. This 
element is also found in combination in a large number 
of substances in nature. It is found in the nitrates, as 
saltpetre or potassium nitrate, KNO^ , and Chili saltpetre 
or sodium nitrate, NaNOg. It is also found in the form 
of ammonia, which is a compound of nitrogen and 
hydrogen of the formula NH3. Ammonia occurs in small 
quantity in the air, and is formed under a variety of con- 
ditions, which will be referred to when the substance is 
considered. Nitrogen occurs, further, in most animal 
substances in chemical combination. 

Preparation of Nitrogen. — The most convenient way to 
prepare nitrogen is to burn a piece of phosphorus in a 
bell-jar over water. The reasons why phosphorus is better 
for the purpose than most other substances are (1) because 
it burns, that is combines with oxygen, easily; and (2) 
because the compound which it forms with oxygen (the 
product of combustion) is a solid and dissolves in water. 

Experiment 27.— Place a wide-mouthed jar over water in a 
larger vessel of water. In the middle of a flat cork about three 
inches in diameter fasten a small porcelain crucible, and float 
thia on the water in the trough. Put into it a piece of phosphorus 

39 



40 THE ELEMENTS OF CHEMISTRY. 

about twice the size of a pea, and set fire to the phosphorus. 
Quickly place the jar over it on a support which will prevent the 
jar from sinking more than an inch or two in the water. At first 
some air will be driven out of the vessel on account of the expan- 
sion due to the heat. After the burning has stopped cover the 
mouth of the jar with a glass plate and turn it mouth upward. 
Try the effect of introducing successively several burning bodies 
into the nitrogen, as, for example, a candle, a piece of sulphur, 
phosphorus, etc. 

Other Substances besides Phosphorus may be Used. — 

Anything that has the power to combine with oxygen may 
be used in the preparation of nitrogen from the air. 
Metallic copper is convenient, and is sometimes used. It 
is only necessary to pass air over heated copper, when the 
metal combines with oxygen, forming the solid copper 
oxide, CuO, leaving the nitrogen uncombined. 

Properties of Nitrogen. — You have seen that nitrogen 
is a colorless, tasteless, inodorous gas. At very low tem- 
perature and under high pressure it is transformed into a 
liquid. It does not support combustion, nor does it burn. 
[Suppose nitrogen were combustible, how would this affect 
the composition of the atmosphere ?] Nitrogen not only 
does not combine with oxygen readily, but it does not com- 
bine with any other element easily except at a very high 
temperature, and then with only a few. Just as it does not 
support combustion, so also it does not support breathing. 
An animal would die in it, not on account of any active 
poisonous properties possessed by it, but on account of a 
lack of oxygen. In the air it serves the useful purpose of 
diluting the oxygen. If the air consisted only of oxygen, 
ail processes of combustion would certainly be much more 
active than they now are. What the effect on animals of 
the continued breathing of oxygen would be it is difficuU 



NITROGEN. 41 

to say, as but few experiments on this subject have been 
made. 

Nitrogen and Oxygen are Mixed together, not Chem- 
ically Combined in the Air. — It is not an easy matter to 
prove this statement satisfactorily, but the evidence is so 
strong that no chemist doubts it. 

(1) If nitrogen and oxygen are mixed together, the 
mixture acts like air. When they are mixed there is 
nothing to show that chemical action takes place. You 
have seen that the combination of two substances gives 
rise to changes in temperature. When nitrogen and 
oxygen are mixed together there is no change in the tem- 
perature of the gases. . 

(2) Substances known to be chemical compounds do 
not vary in composition; that of the air does vary slightly. 

(3) Air dissolves somewhat in water. If air which has 
been thus dissolved is pumped out and analyzed, it is 
found to have a composition different from that of ordinary 
air. Instead of containing 1 volume of oxygen to 4 
volumes of nitrogen, it will contain 1 volume of oxygen 
to 1.87 volumes of nitrogen. The relative quantity of 
oxygen is much larger in air which has been dissolved in 
water than in ordinary air. This is due to the fact that 
oxygen dissolves more readily in water than nitrogen does. 
If the gases were in chemical combination the compound 
would probably dissolve without change of composition. 

Liquid Air. — It has been stated that both oxygen and 
nitrogen can be converted into liquids by subjecting them 
to high pressure and low temperature. As air is a mixture 
of these two elements, it follows that it can be liquefied. 
By subjecting it to high pressure and then letting it 



42 THE ELEMENTS OF CHEMISTRY, 

escape through a very small opening it is cooled to a low 
temperature. If this cold air is allowed to play upon the 
vessel containing the compressed air the latter is partly 
liquefied. Very efficient machines have been constructed 
by which air can be liquefied in any desired quantity. 
The problem of its practical application has not yet been 
worked out. 

Oxygen Prepared from Liquid Air. — When liquid air is 
allowed to stand under the ordinary pressure of the 
atmosphere the nitrogen boils off with some of the oxygen, 
and after a time nearly pure liquid oxygen is left. This 
furnishes a method of obtaining oxygen from the air. 
(Liquid nitrogen boils at — 196° C. Liquid oxygen boils 
at - 181° C, or 13° higher.) 

Argon. — When nitrogen obtained from the air as above 
described is carefully examined it is found to contain about 
1 per cent of another gaseous substance that is so much 
like nitrogen that it escaped detection until a few years 
ago (1894). It is called argon, from a Greek word signify- 
ing idle. This name was given to it because- it cannot be 
made to combine with any other element. What part it 
plays in the air, if any, is not known. 

Summary. — The air consists of nitrogen and oxygen in 
the proportion of 4 volumes of the former to 1 volume of 
the latter. Oxygen supports combustion; nitrogen does 
not. Oxygen supports respiration; nitrogen does not. 
Oxygen and nitrogen are elements. They are not 
chemically combined in the air. Oxygen is made by heat- 
ing certain substances which contain it, as, for example, 
mercury oxide and potassium chlorate. Nitrogen is made 
by burning phosphorus in a closed vessel containing air. 



NITROGEN. 43 

Elements combine in definite proportions by weight 
(law of definite proportions). 

In each element a number may be selected by means of 
which the proportion by weight in which it enters into 
combination may be expressed (combining weights). 

If an element combines with another in more than one 
proportion, the quantities which enter into combination 
with a fixed quantity of the second element bear a simple 
ratio to one another (law of multiple^roportions). 



CHAPTEE VI. 

WATER. 

Occurrence of Water in Nature. — The wide distribution 
of water on the earth is familiar to every one. But water 
also occurs in forms and conditions which prevent it from 
being easily recognized. Thus, all living things contain 
a large proportion of water, which can be driven off by 
heat. If a piece of wood or a piece of meat is heated, 
water passes off. 

Experiment 28.— In a dry tube heat gently a small piece of 
wood. "What evidence do you obtain that water is given off ? 
Do the same thing with a piece of fresh meat. 

Large Proportion of Water in Animal and Vegetable 
Substances. — The proportion of water in animal and 
vegetable suj3stances is very great. If the body of a man 
weighing 150 pounds were put into an oven and thoroughly 
dried there would be left only about- 50 pounds of solid 
matter, all the rest being water. As all meat, vegetables, 
and foodstuffs in general contain a similar large propor- 
tion of water, it is evident that water is an important 
article of commerce. When you buy four pounds of beef 
you pay for about three pounds of water and one pound 
of solid matter. 

44 



IVATER. 45 

Water of Crystallization. — Many chemical compounds 
when deposited from solutions in water often appear in 
regular forms called crystals. These frequently enclose 
water in chemical combination, and this water is necessary 
in order that the substance may exist in the form of 
crystals. Water thus held in combination is called water 
of crystallization. 

Experiment 29. — Dissolve some ordinary alum in water (6-8 
ounces alum to 200 c.c. water) by the aid of heat. Filter 
through a plaited filter and allow the filtered solution to cool. 
Crystals of alum will be deposited. Pour off the liquid above 
and place a few of the crystals on a piece of dry filter-paper. 
After the water is all absorbed from them and they appear dry, 
put them in a dry test-tube and heat gently, l^hat evidence 
have you that water is contained in the crystals ? 

Experiment 30. — Heat a piece of gypsum, which is the natural 
substance from which " plaster of Paris " is made. Does it con- 
tain water of crystallization ? 

Experiment 31. — Heat gently a few small crystals of copper 
sulphate or "blue vitriol." In this case the loss of water is 
accompanied by a loss of color. After all the water is driven off, 
the powder left behind is white. On dissolving it in water, how- 
ever, the solution will be seen to be blue ; and if this solution is 
evaporated until the substance is deposited, it will appear in the 
form of blue crystals. 

Efflorescent and Deliquescent Substances.^Some sub- 
stances that contain water of crystallization give it up 
very easily when exposed to the air. Such substances are 
called effloresc€7it. 

Experiment 32. — Select a few crystals of sodium sulphate or 
Glauber's salt which have not lost their lustre. Put them on a 
watch-glass, and let them lie exposed to the air for an hour or 
two. They soon lose their lustre, and become white and powdery 
on the surface. Try the same experiment with sodium carbonate 
or crystallized soda. 



46 THE ELEMENTS OF CHEMISTRY. 

Some compounds if deprived of their water of crystal- 
lization will take it up again when allowed to lie in an 
atmosphere containing moisture. Substances that take 
up water from the air and dissolve in this water are called 
deliquescent. As the air always contains moisture, it is 
only necessary to expose such compounds to the air in 
order to notice the change. It is well shown by the com- 
pound calcium chloride, CaCl2. This substance has a 
remarkable power of attracting water and holding it in 
combination. 

Experiment 33. — Expose a few pieces of calcium chloride to 
the air. Its surface will soon give evidence of being moist, and 
after a time the substance will dissolve in the water which is 
absorbed. 

Water is a Compound. — That water is a compound and 
not an element can be shown by passing an electric current 
through it. If the ends of the wires connected with a 
galvanic battery are put in water a short distance apart it 
will be noticed that bubbles of gas rise from each wire. 
As these gases cannot well come from the wires, the most 
probable supposition is that they are formed from the 
water. 

Experiment 34. — To the ends of the copper wires connected 
with two cells of a Bunsen's or Grove's battery fasten small plati- 
num plates, say 25 mm. (1 inch) long by 12 mm. (-| inch) wide. 
Insert these platinum ends into water contained in a glass vessel 
about 15 cm. (6 inches) wide and 7 to 8 cm. (3 inches) deep, 
taking care to keep them separated from each other. No action 
^ill take place, for the reason that water will not conduct elec- 
tricity, and hence when the platinum ends are kept apart there is 
uo current. By adding to the water about one tenth its own 
volume of strong sulphuric acid it acquires the power to conduct 
electricity. It will then be observed that bubbles rise from each 
©^ the platinum plates. In order to collect the gases the ap- 



IVATER, 



47 




paratus may be arranged as shown in Fig. 10. 1i and o represent 
glass tubes which may conveniently be about 30 cm. (1 foot) 
long and 25 mm. (1 inch) internal diameter. They should be 
marked by means of a file, or by etching, 
so that equal divisions can be recognized. 
Tubes thus marked so that the divisions 
indicate cubic centimetres are most con- 
venient, and are easily obtained of dealers 
in chemical apparatus. The tubes are 
first filled with the water containing about 
one tenth its volume of sulphuric acid, 
and then placed with the mouth under 
water in the vessel A. The platinum ends 
are now brought beneath the inverted 
tubes. The bubbles will rise in them and 
displace the w^ater. Gradually the water 
will be completely forced out of one of the 
tubes, while the other is still half full of 
water. The substance which we have thus 
collected in each of the tubes is an invis- 
ible gas. After the first tube is full of 
gas, remove it by placing your thumb over 
the mouth. Turn it mouth upward, and at once apply a lighted 
match to it. A flame will be noticed. The gas hums. Is it 
air ? Is it oxygen ? Is it nitrogen ? In the mean time the 
second tube will have become filled with gas. Remove the tube 
in the same way, and insert a thin piece of wood with- a spark on 
the end. Does this gas act like oxygen ? The gas collected in 
the tube which first became filled is known as hydrogen., while 
the other is oxygen. 

What the Experiment Shows. — The experiment just 

performed shows that when an electric current is passed 

through water hydrogen and oxygen are obtained, and also 

that there is obtained twice as much hydrogen by bulk as 

oxygen. Whether these are the only elements contained 

in water can only be shown by further experiments. But 

it will be necessary first to learn something about 

hydrogen. 



Fig. 10, 



CHAPTEE VII. 
HYDROGEN. 

Occurrence of Hydrogen. — Hydrogen is found in nature 
very widely distributed^ and in large quantity. It forms 
one ninth, the weight of water, and is contained in all the 
principal substances that enter into the composition of 
plants and animals. 

Preparation of Hydrogen. — It can be obtained 

(a) By decomposition of water by means of the electric 
current ; 

(b) By decomposition of water by means of certain 
metals ; 

(c) By the action of substances known as acids on 
metals. 

The first method has already been illustrated in Experi- 
ment 34. 

Experiment 35. — Throw a small piece of sodium * on water. 
Cover the vessel with a piece of cardboard. While it is floating 
on the surface apply a lighted match to it. What takes place ? 

* The metals sodium and potassium are kept under kerosene oil. 
When a small piece is wanted, take out one of the larger pieces 
from the bottle, roughly wipe off the oil with filter-paper, and cut 
off a piece the size needed. It is not advisable to use a piece larger 
than a small pea. Dry your fingers before handling these metals, 

48 



HYDROGEN. 



49 



The flame is due to burning hydrogen, the flame being colored 
yellow by the presence of sodium, some of which also burns. 

Experiment 36. — Certain metals that do not decompose water 
at ordinary temperatures, or that decompose it slowly, decom- 
pose it easily at elevated temperatures. This is true of iron. If 
steam is passed through a tube containing pieces of iron turn- 
ings or fine bright iron wire heated to redness, the w^ater is de- 
composed, the oxygen is retained by the iron in chemical combi- 
nation, while the hydrogen is liberated. In this experiment a 
porcelain tube with an internal diameter of from 20 to 25 mm. 
(about an inch) and a gas-furnace are desirable, though a hard 
glass tube and a charcoal-furnace will answer. The arrangement 
of the apparatus is shown in Fig. 11. 




Fia. 11. 



Water-gas. — Many other substances have the power to 
decompose water and set hydrogen free. The fact that a 
combustible gas can be obtained from w^ater has led to 
many attempts to manufacture gas for heating and illumi- 
nating purposes from water. There is, however, no cheap 
substance which has the power to decompose water at 
ordinary temperatures. Heat must be used, and it is 
generally the case that the quantity of heat required to 
effect the decomposition is greater than that which would 
be obtained by burning the hydrogen formed. The 



50 THE ELEMENTS OF CHEMISTRY. 

so-called ^^ water-gas '^ now so extensiyely manufactured 
in the United States both for illuminating and heating is 
made by the action of highly heated hard coal on steam. 
The essential part of the chemical reaction is represented 
by the equation 

C + H^O = CO + 2H. 

Carbon (or coal) acting upon the water (H.O) combines 
with the oxygen, forming the compound carbon monoxide. 
CO, and leaving the hydrogen uncombined. Both j)rod- 
ucts are gases, and both burn; and when this mixture is 
enriched by some of the oils obtained from petroleum it 
burns well and gives a good light. 

The Common Acids. — Hydrogen is most conveniently 
made in the laboratory by treating a metal with an .acid. 
As will be seen later, acids are substances that contain 
hydrogen, and that give up this hydrogen very easily. 
Among the common acids found in every laboratory are 
liydrocliloric acicl^ suljjJiun'c acid, and nitric acid. These 
compounds will be treated of farther on. 

Hydrogen is Generally Given off when a Metallic Ele- 
ment Acts upon an Acid. — This is shown as follows : 

Experiment. 37. — Always he cautious in worMng ivitli hydro- 
gen. The danger consists in the fact that a mixture of hydro- 
gen and oxygen or of hydrogen and air is extremely explosive. 
It requires a sjJarJc or aflame to exjjlode it. Always let the gas 
esccqje for a time^ and collect a test-tube fidl hy displacement of 
icater and then light it to see if it ivill burn quietly^ before apply- 
ing aflame to the gas issuing from the generating vessel. — In a 
cyUnder or test-tube put some small pieces of granulated zinc^ 
and pour upon it enough ordinary hydrochloric acid to cover it. 
TVhat do you notice ? After the action has continued for a 
minute or two apply a lighted match to the mouth of the vessel. 
^hat takes place ? Try the same experiment with sulphuric acid 



HYDROGEN, 



51 



diluted with six times its volume of water.* AYhat is the result ? 
The gas given off is hydrogen. For the purpose of collecting it 
the operation is best performed in a bottle with two necks called 
a Woulff 's flask (see Fig. 12), or in a wide-mouthed bottle in which 
is fitted a cork with two holes (see Fig 13). Through one of the 
holes passes a funnel-tube, and through the other a glass tube 





Fig. 12. 



Fig. 13. 



bent in a convenient form. Put a small handful of granulated 
zinc into the bottle and pour upon it enough of a cooled mixture 
of sulphuric acid and water (1 volume concentrated acid to 6 
volumes of water) to cover it. Usually a brisk evolution of gas 
will take place at once. Wait two or three minutes, and then 
collect some of the gas by displacement of water. Should the 
action become slow add a little more of the dilute acid. It will 
be well to fill several cylinders and bottles with the gas. 

* If it is desired to dilute ordinary concentrated sulphuric acid 
with water, the acid should be poured slowly into the water while 
the mixture is constantly stirred. If the water is poured into the 
acid, the heat evolved at the places where the two come in contact 
may be so great as to convert the water into steam and cause the 
strong acid to spatter. 



52 



THE ELEMENTS OF CHEMISTRY. 



Physical Properties of Hydrogen. — Hydrogen is a color- 
less, inodorous, tasteless gas. Made by the action of zinc 
on acids, it lias a slightly disagreeable odor. This is due 
to the presence of small quantities of impurities. If these 
are removed the odor disappears. 

Experiment 38. — Pass some of the gas through a solution of 
potassium 2:>ermanganate ; collect some of it, and notice, whether 
it has an odor. The apparatus should be arranged as shown in 
Fig. 14. The solution of potassium permanganate is, of course, 
contained in the small cylinder, J., and the tubes so arranged that 
the gas bubbles through it. 

The gas is not poisonous, and may therefore be inhaled 
with impunity. We could not, however, live in an atmos- 





SG 



Fig. 14. 

phere of hydrogen, as we must have oxygen. It is the 
lightest siibstance known, being fourteen and a half times 
lighter than air and sixteen times lighter than oxygen. 

Experiment 39. — Place a vessel containing hydrogen with the 
mouth upward and uncovered. In a short time examine the gas 
and see whether it is hydrogen. 



HYDROGEN, 



53 




Experiment 40. — Gradually bring a vessel containing hydro- 
gen with its mouth upward below 
an inverted vessel containing 
air, in the way shown in Fig. 15. 
The air will be displaced. On 
examination, the inverted vessel 
will be found to contain hydro- 
gen, while the one with the mouth 
upward will contain none. The 
gas is thus poured upward. ^^^- ^^• 

Experiment 41. — Soap-bubbles filled with hydrogen rise in the 
air. The experiment is best performed by connecting an ordi- 
nary clay pipe by means of a piece of rubber tubing with the 
exit-tube of a gasometer filled with hydrogen. Small balloons of 
collodion are also made for showing the lightness of hydrogen. 
Large balloons are always filled with hydrogen or some other 
light gas. Some kinds of illuminating-gas are rich in hydrogen, 
and may therefore be used for the purpose. 

Weight of Hydrogen Compared with that of Oxygen. — 
A litre of hydrogen at 0° C. and under the pressure of the 
atmosphere weighs 0.08995 gram. A litre of oxygen under 
the same conditions w^eighs 1.429 grams. These figures 
are to each other as 1 to 16. But the figures 1 and 16 are 
the combining weights of hydrogen and oxygen; that is 
to say, they are the figures best adapted to expressing the 
relative weights of these elements that enter into combina- 
tion. A similar connection exists betw^een the relative 
weights of equal volumes of some other elementary gases 
and their combining weights, as will be seen later. 

All Combining Weights are Referred to that of Hy- 
drogen. — The figures called the combining weights express 
the relations between the weights of the different elements 
which enter into combination. When we say that the 
combining weight of hydrogen is 1 and that of oxygen is 
16, w^e mean that tjie weight of oxygen which generally 



54 THE ELEMENTS OF CHEMISTRY. 

enters into combination is sixteen times as great as the 
weight of hydrogen which enters into combination. The 
figures 2 and 32 would express this relation just as well; 
so would 6^ and 100; but the simplest figures that can be 
used are 1 for hydrogen and 16 for oxygen. Having 
adopted these^ all other combining weights are referred to 
these. 

Hydrogen a Liquid. — At a very low temperature and 
high pressure hydrogen becomes liquid. This liquid boils 
at - 2br C. 

Chemical Properties of Hydrogen. — Under ordinary 
circumstances hydrogen is not a particularly active ele- 
ment. It does not unite with oxygen at ordinary tem- 
peratures^ but, like wood and most other combustible 
substances, needs to be heated up to its kindling tempera- 
ture before it will burn. You have seen that it burns if 
a lighted match is apjDlied to it. The flame is colorless 
or slightly blue. As burned under ordinary circumstances 
the flame is colored, in consequence of the presence of 
foreign substances; but that it is colorless when the gas is 
burned alone can be shown by burning it 
from a platinum tube, which is itself not 
acted upon by the heat. 

Experiment 42. — If there is no small platinum 
tube available, roll up a small piece of platinum- 
foil and melt it into the end of a glass tube, as 
shown in Fig. 16. Connect the burner thus made 
with a bottle or gasometer containing hydrogen, 
and after the gas has been allowed to issue from 
it for a moment * set fire to it. In a short time 
it will be seen that the flame is practically color- 
less and gives no light. That it is hot is shown by holding a 
piece of platinum wire or a piece of some other metal in it. 
^ Be cautious. See Experiment 37. 




HYDROGEN, 



55 



The Burning of Hydrogen. — Hydrogen burns. You 
have already learned that burning consists in combining 
with oxygen. On the other hand, substances that burn 
in the air are extinguished when put in a vessel containing 
hydrogen. This is the same as saying 
that a body which is combining with 
oxygen does not continue to combine 
with oxygen when it is put in an atmos- 
phere of hydrogen, and does not com- 
bine with hydrogen. This is expressed 
by saying that hydrogen does not support 
combustion. 

Experiment 43.— Hold a wide-moutbed bot- 
tle or cyliiidej filled with hydrogen with the 
mouth downward. Insert into the vessel a 
lighted taper held on a bent wire, as shown 
in Fig. 17. The gas takes fire at the mouth 
of the vessel, but the taper is extinguished. 
On withdrawing the taper and holding the wick for a moment 
in the burning hydrogen, it will take fire if there is a spark in 
it, but on putting it back in the hydrogen it will again be ex- 
tinguished. Other burning substances should be tried in the 
same way. 




Fig. 17. 



CHAPTER VIII. 

WATER (Continued), 

Composition of Water. — In Chapter VI you learned that 
hydrogen and oxygen are both set free when an electric 
current is passed through water containing a little sul- 
phuric acid. It remains to be seen whether these are the 
only elements contained in water. If water consists only 
of hydrogen and oxygen, then when these elements com- 
bine water should be formed. But hydrogen combines 
with oxygen when it burns. Is water formed when 
hydrogen burns ? 

Experiment 44. — Pass hydrogen from a generating-flask or a 
gasometer through a tube containing some substance that will 
absorb moisture, for all gases collected over water are charged 
with moisture. You have seen in Experiment 33 that calcium 
chloride has the power to absorb moisture. It is extensively used 
in the laboratory for the purpose of drying gases, and it may be 
used in the present experiment. It should be in small pieces 
about the size of a pea, not powdered. After passing the hydro- 
gen through the calcium chloride, pass it through a tube ending 
in a narrow opening and set fire to it. (Take the precaution 
mentioned in Experiment 37, page 50.) If now a dry vessel is 
held over the flame, drops of water will condense on its surface 
and run down. A convenient arrangement of the apparatus is 
shown in Fig 18. A is the calcium chloride tube. Before light- 
ing the jet hold a glass plate in the escaping gas, and see whether 
water is deposited on it. Light the jet before putting it under the 
^ell-jar ; otherwise, if hydrogen is allowed to escape into the ves- 

56 



IVATER, 



57 



sel it will contain a mixture of air and hydrogen, and this mix- 
ture, as has been stated, is explosive. 




Fig, 18. 

Hydrogen and Oxygen do not Combine at the Ordinary 
Temperature. — If they did, hydrogen would take fire the 
moment it comes in contact with the air. If we mix the 
gases together and allow the mixture to stand unmolested, 
it remains unchanged. If, however, we should bring a 
spark or a flama in contact with the mixture a violent 
explosion would occur, and a careful examination would 
show that the explosion is caused by the combination of 
the two gases. The combination causes heat. The heat 
causes the gases to expand greatly and suddenly, and the 
noise is caused by this sudden expansion. The expansion 
is followed by a contraction. 

Experiment 45. — Mix hydrogen and oxygen in the proportion 
of about 2 volumes of hydrogen to 1 volume of oxygen in a gas- 
ometer or large bottle. Fill soap-bubbles, made as directed in 
Experiment 41, with this mixture and allow them to rise in the 
air. As each one rises bring a lighted taper in contact with it, 



5 8 THE ELEMENTS OF CHEMISTRY. 

when a sharp explosion will occur. Great care must be taken to 
keep all flames away from the neighborhood of the vessel con- 
taining the mixture. 

Measuring the Volumes of Hydrogen and Oxygen that 
Combine to Form Water. — The last experiment simply 
showed that when a flame comes in contact with a mixture 
of hydrogen and oxygen an explosion occurs. To show 
what else takes place the experiment must be performed 
in a closed vessel. This experiment has been performed 
many times. As it would be difficult for you to repeat it 
you will have to be satisfied with a description of the 
apparatus used and a statement of the result obtained. 
A tube is used which is marked on the outside so that the 
volume of gases contained in it can be seen. This tube 
has tM^o small platinum wires passed through it at the 
closed end, nearly meeting inside and ending in 
loops outside, as shown in Fig. 19. It is called a 
eudiometer. It is filled with mercury and inverted 
in a trough containing mercury. A quantity of 
pure hydrogen is now passed up into the tube and 
its volume accurately measured. Then just half 
this volume of oxygen is introduced, and after 
the mixture has stood for a few minutes, so that 
the gases can become thoroughly mixed, an elec- 
tric spark is passed between the wires inside the 
tube by connecting the loops with the poles of a 
small Kuhmkorff coil or with a Leyden jar. The 
explosion takes place noiselessly and with very 
little danger. If the interior of the tube was dry 
Fig. 19. bcforc the explosion, it will be seen to be moist 
afterwards. The liquid water v/hich is formed occupies 



IVATER, 59 

almost no space as compared with the space occupied by 
the two gases before combination. Now, if the experi- 
ment is performed with the two gases in different i)ropor- 
tions, it will be fonnd that only when they are mixed in 
the proportion of 2 volumes of hydrogen to 1 volume of 
oxygen do they completely disappear when exploded. If 
there is a larger proportion of hydrogen present, the 
excess is left over. If there is a larger proportion of 
oxygen present, the excess of oxygen is left over. Thus 
it is shown that when hydrogen and oxygen combine to 
form water, they do so in the proportion of 2 volumes of 
hydrogen to 1 volume of oxygen. 

Formation of Water by Passing Hydrogen over Heated 
Oxides. — Water can be formed by passing hydrogen over a 
compound containing oxygen and heating. A convenient 
substance for the purpose is the compound of copper and 
oxygen known as copper oxide or black oxide of copper. 
It contains its elements in the proportion represented by 
the formula CuO. At ordinary temperature hydrogen 
does not act upon this substance. At a high temperature 
the hydrogen combines with the oxygen, forming water, 
and the copper is left behind as such. The reaction is 
represented thus : 

CuO + 2H = H,0 + Cu. 

Experiment 46.— Arrange an apparatus as shown in Fig. 20. 
^ is a Woulff's flask for generating hydrogen. To remove im- 
purities the gas is passed through a solution of potassium per- 
manganate contained in the wash-cylinder B. The U tube C 
contains granulated calcium chloride, and the cylinder D contains 
concentrated sulphuric acid, both of them serving to remove 
moisture from the glass. The pure dry hydrogen is now passed 
through the hard glass tube E^ which contains a layer of copper 



6o 



THE ELEMENTS OF CHEMISTRY, 



oxide. After the aiyparatus is filled ivitTi liydrogen the burner 
iiiider E is lighted, and the copper oxide heated to low redness. 




Fig. 20. 

Soon moisture will be seen in the end of the tube and drops of 
water will collect in the vessel G. 

How this Experiment Shows the Composition of Water. 

— The coj^per oxide loses its oxygen and of course loses 
weight. If, therefore, yon should weigh the copper oxide 
before the experiment, and afterward the copper, and 
should also collect and weigh the water formed, you could 
from the figures obtained calculate the relative weight of 
oxygen contained in water, thus : 

Let X = weight of tube + copper oxide before the experiment ; 

y = weight of tube + copper after the experiment. 
Then x — y = weight of oxygen taken from the copper oxide. 

The water formed can be collected in a small tube con- 
taining calcium chloride. 

Let a = weight of calcium chloride tube before ; 

h = weight of calcium chloride tube after. 
Then 6 — a = weight of water formed. 



IVATER, 6 1 

If the experiment is carefully performed, it will be 

^ y 

found that ^^ is very nearly equal to f, which means 

that by weight oxygen forms eight ninths of water. 

Oxidation and Reduction. — Any substance which like 
hydrogen has the power to abstract oxygen from com- 
pounds containing it is called a reducing agent. The 
process of abstracting oxygen from a compound is called 
reduction. Reduction and oxidation are opposite processes. 

Applications of the Heat Evolved by the Combination of 
Hydrogen and Oxygen. — The heat evolved when hydrogen 
combines with oxygen is very great, and it is utilized for 
various purposes. To burn hydrogen in the air is, as we 
have seen, a simple matter, but to burn it in oxygen 
requires a special apparatus to prevent the mixing of the 
gases before they reach the end of the tube where the 
combustion takes place. The oxyliydrogen lloiopijpe 
answers this purpose. It is a tube with a smaller tube 
passing through it, as shown in Fig. 21. 




FiQ. 21. 

The hydrogen is admitted through a^ and the oxygen 
through 5. It will be seen that they come together only 
at the end of the tube. The hydrogen is first passed 
through and lighted; then the oxygen is passed through 
slowly, the pressure being increased until the flame 
appears thin and straight. It gives very little light, but 
it is intensely hot. 



62 THE ELEMENTS OF CHEMISTRY, 

Experiment 47. — Hold in the flame of the oxyhydrogen blow- 
pipe successively a piece of iron wire, a piece of a steel watch- 
spring, a piece of copper wire, a piece of zinc, a piece of platinum 
wire. 

The Oxyhydrogen Blowpipe Used in Working Plati- 
num. — The metal platinum is used for many purposes, 
particularly for making chemical apparatus. The vessels 
are made from molten platinum, and the metal is melted 
by means of the oxyhydrogen blowpipe. 

The Lime-light or Drummond Light. — When the flame 
of the oxyhydrogen blowpipe is made to strike against 
some substance which it cannot melt nor burn up, the 
substance becomes heated so high that it gives off intense 
light. The substance commonly used is quicklime. 
Hence the light is sometimes called the lime-light. It is 
also known as the Drummond light or calcium light. 

Experiment 48. — Cut a piece of lime of convenient size and 
shape, say an inch long by three quarters of an inch wide and the 
same thickness. Fix it in position so that the flame of the oxy- 
hydrogen blowpipe will strike upon it. The light is very bright, 
but by no means as intense as the electric light. 

Properties of Water. — Though, as we know, water is 
widely distributed over the earth, it is never found per- 
fectly pure. All natural waters contain foreign substances 
in solution. These substances are taken up from the air 
or from the earth. Pure water is tasteless and inodorous. 
In thin layers it is colorless, but in thick layers it is blue. 
This has been show^n in the laboratory by filling a long 
tube wdth distilled water. When looked through it 
appears blue. The beautiful blue color of some mountain 
lakes is the natural color of pure w^ater. 

On cooling water contracts until it reaches the tempera- 



IVATER, 6^ 

ture of 4° C. At this point it has its maximum density. 
When cooled below 4° it expands, and the specific gravity 
of ice is somewhat less than that of water. Hence ice 
floats on water. 

Natural Waters. — The purest water found in nature is 
rain-water, particularly that which falls after it has rained 
for some time. That which first falls always contains 
impurities from the air. As soon as the rain-water comes 
in contact with the earth and begins its course toward the 
sea it begins to take up various substances, according to 
the character of the soil with which it comes in contact. 
Mountain streams which flow over rocky beds, particularly 
beds of sandstone, which is very insoluble in water, con- 
tain exceptionally pure water. Streams which flow over 
limestone dissolve some of the stone, and the water 
becomes ^^hard.^^ The many varieties of mineral springs 
have their origin in the presence in the earth of certain 
substances which are soluble in water. Common salt 
occurs in large quantities in different parts of the earth. 
As it is easily soluble in water, many streams contain it; 
and as all the streams find their way into the ocean, you 
see one reason why the water of the ocean is salt. 

EflFervescent Waters are such as contain some gas, 
usually carbonic-acid gas, in solution and give up a part 
of it when placed in open vessels. 

Chalybeate Waters contain some compound of iron. 

Sulphur-water contains a compound of hydrogen and 
sulphur, called hydrogen sulphide or sulphuretted hy- 
drogen (which see). 

Impure Waters. — As streams approach the habitations 
of man they are likely to become contaminated. The 



64 THE ELEMENTS OF CHEMISTRY. 

drainage (called sewage) from the neighborhood of human 
dwellings is very apt to find its way into a near stream. 
This condition of things is most strikingly illustrated by 
the case of a large town situated on the banks of a riyer. 
It often happens that the water of the river is used for 
drinking purposes, and it also happens that the water is 
contaminated by sewage. Water when once contaminated 
by sewage tends to become pure again by contact with the 
air in consequence partly of the action of the oxygen. 
Hence river-water may become fit for use after having 
been impure. If it is to be used for drinking purposes, 
however, it is not well to rely too much upon this process 
of purification. 

Wells should not be dug too near dwellings and farm- 
houses, as the sewage may find its way into them beneath 
the surface of the earth. This is a frequent source of 
danger, as some diseases are communicated from one 
person to another by means of contaminated drinking- 
water. 

Distillation. — Water can be purified by means of dis- 
tillation. This consists in boiling the water, and then 
condensing the vapor by passing it through a tube kept 
cool by surrounding it with cold water. By means of dis- 
tillation most substances in solution in water can be got 
rid of. Volatile substances, however, wall of course pass 
over with the water vapor. Aboard ship salt water is 
distilled and thus made fit for drinking. In chemical 
laboratories ordinary water is distilled in order to purify 
it for fine work with chemical substances. A simple 
apparatus to illustrate the process of distillation is that 
shown in Fig. 22. 



IVATER. 



65 



The water to be distilled is placed in the flask A, The 
flask is connected by means of a bent glass tube B with 
the long tube C, This in turn is surrounded by the 
larger tube or jacket D. The side tube E is connected 
with a faucet by means of the rubber tube G. The water 
is allowed to flow slowly into the jacket and out at F^ 
whence it passes through the rubber tube H to the sink. 
When the water in A is boiled, the vapor passes into the 




Fig. 22. 

tube C. Here it is cooled down, and takes the form of 

liquid, which runs down and collects in the flask K called 

the "receiver. The apparatus therefore consists of three 

parts: the distilling -flask ^ the condenser, and the receiver. 

Experiment 49. — Dissolve some copper sulphate, or some other 
colored substance, in a litre of water, and distil the water. 

Water as a Solvent. — It is known that many solids, 
liquids, and gases when brought into water disappear and 
form colorless liquids that look like water. Some give 
colored liquids of the same color as the dissolved sub- 
stance, and others give liquids that have colors quite 
different from the dissolved siibstauces, Oii the other 



66 THE ELEMENTS OF CHEMISTRY. 

hand there are many substances that do not dissolve in 
water. If a very small quantity of substance is dissolved 
in a large quantity of water, and the solution thoroughly 
stirred, the dissolved substance is uniformly distributed 
throughout the liquid and remains so. That the dissolved 
substance is everywhere present in the solution can be 
shown, further, by the aid of certain dye-stuffs, as, for 
example, magenta. A drop of a concentrated solution of 
this substance brought into many gallons of water imparts 
a distinct color to all parts of the liquid. An experiment 
of this kind gives some idea of the extent to which the 
subdivision of matter can be carried. For it is evident 
that in each drop of the dilute solution some of the color- 
ing matter must be contained, though the quantity must 
be extremely small. While there seems to be no limit to 
the extent to which a solution can be diluted, and still 
retain the dissolved substance uniformly distributed 
through its mass, there is a limit to the amount of every 
substance that can be brought into solution, and this 
varies with the temperature, and, in the case of gases, with 
the pressure. Some substances are easily soluble; others 
are difficultly soluble. When the solutions are boiled the 
water passes off and leaves the dissolved substance behind, 
if it is a non-volatile solid. 

Solutions and Chemical Compounds. — Solutions, in gen- 
eral, seem to differ from true chemical compounds in 
some important particulars, and also from mechanical 
mixtures. Definiteness of composition is a common char- 
acteristic of chemical compounds, but solutions have no 
definite composition. Any quantity of a substance, from 
the minutest particle to a certain fixed quantity for any 



IVATER. 67 

given temperature, can be dissolved, and the solution 
formed is in each case uniform and aj)pears to be a perfect 
solution. 

Solution as an Aid to Chemical Action. — When it is 
desired to secure the chemical action of one solid substance 
upon another it is often found advantageous to bring them 
together in solution. The full explanation of this remains 
to be given. It appears highly probable that when a sub- 
stance is dissolved in water some deep-seated change takes 
place in it, and that is the principal reason why substances 
in solution act upon each other so readily. This subject 
will be briefly discussed farther on. 

Summary. — You have thus learned that 

(1) Water can be decomposed into hydrogen and 
oxygen by means of an electric current; 

(2) The gases are obtained in the proportion of eight 
parts by weight of oxygen to one part by weight of 
hydrogen, or one volume of oxygen to two volumes of 
hydrogen ; 

(3) When hydrogen is burned water is formed; 

(4) When hydrogen and oxygen are mixed together 
they do not combine under ordinary circumstances; 

(5) When a spark or flame is brought in contact with 
the mixture, violent action accompanied by explosion 
takes place; 

(6) This action accompanies the chemical combination 
of the two gases; 

(7) They combine in the same proj^ortions as those in 
which they are obtained from water by the action of the 
electric current j 



6S THE ELEMENTS OF CHEMISTRY. 

(8) Water can be made by passing hydrogen over heated 
copper oxide; 

(9) By weighing the copper oxide before and after the 
experiment, and determining the weight of the water 
formed, it is found that eight ninths of the weight of the 
water is oxygen. 

Formula of Water. — All the facts taken together prove 
that the composition of water is what it has been stated 
to be. Now, using the accepted combining weights of 
hydrogen and oxygen, viz., 1 and 16, the simplest formula 
which expresses the composition of water is H^O. This 
expresses the fact that water is composed of 2 parts by 
weight of hydrogen and 16 parts by weight of oxygen, or 
1 part of the former to 8 parts of the latter. If 8 were 
adopted as the combining weight of oxygen the formula 
of water would be HO. 

Comparison of Hydrogen and Oxygen. — Hydrogen and 
oxygen are different kinds of matter, just as heat and 
electricity are different kinds of energy. Heat can be 
converted into electricity, and electricity into heat, but 
one element cannot by any means known to us be con- 
verted into another. They appear to be entirely inde- 
pendent of each other. If we compare hydrogen with 
oxygen we find very few facts that indicate any analogy 
between the two elements. In their physical properties 
they are, to be sure, similar. Both are transparent, color- 
less, inodorous gases. On the other hand, oxygen com- 
bines readily with a large number of substances with 
which hydrogen does not combine. Oxygen, as you have 
seen, combines easily with carbon^ sulphur, phosphorus, 
and iron, It is a difficult Jii8;t4^^ to g^t any of these 



^ATER, 69 

elements to combine directly with hydrogen. Further, it 
is a general truth that substances that combine readily 
with hydrogen do not combine readily with oxygen. The 
two elements have opposite chemical properties. What 
one can do the other cannot do. 

Opposite Chemical Properties are Favorable to Combina- 
tion. — Not only do hydrogen and oxygen, with their 
opposite properties, combine with great ease under the 
proper conditions, but, as we shall see later, it is a general 
rule that elements of like properties do not readily com- 
bine with one another, while elements of unlike properties 
do readily combine with one another. 

Ozone. — When electric sparks are passed for a time 
through oxygen it is changed in a remarkable way. It 
acquires a strong odor and is much more active than the 
substance which we call oxygen. The odor of the gas is 
noticed in the neighborhood of an electric machine in 
action, and is said to be noticed during thunder-storms. 
The substance which has the odor is ozone. It is formed 
in a number of chemical reactions, as when phosphorus 
acts on air in the presence of water. By cold and pressure 
it has been obtained in the form of a dark-blue liquid. 
Ozone is present in small quantities in the air. 

Eelation between Oxygen and Ozone. — When a certain 
volume of oxygen is converted into ozone the volume of 
gas is decreased to two thirds. 

By heating ozone above 300° C. it is converted into 
ordinary oxygen, and its volume increased from two to 
three. 

It is clear that the element oxygen can be converted 
into something else without the addition of anything to 



70 THE ELEMENTS OF CHEMISTRY. 

it. This might lead you to think that it is not an ele- 
ment. But that which is formed from it has exactly the 
same weight and this can be changed back to oxygen 
without anything being added to it. It follows that the 
change must take place within the oxygen itself. 

Hydrogen Dioxide, H2O2. — Besides water, hydrogen and 
•oxygen form a second compound with each other. This 
is hydrogen dioxide, 1^202-^ It is prepared by treating 
barium dioxide, Ba02 , with sulphuric acid. It is a liquid 
that decomposes easily into water and oxygen. The ease 
with which it gives up oxygen makes it a good oxidizing 
agent. It is now manufactured on a large scale, and is 
used in medicine. 

* The reason for writing this formula HjOa and not HO will be 
seen later. 



CHAPTER IX. 

COMPOUNDS OF NITROGEN WITH HYDROGEN AND 
OXYGEN. 

Destructive Distillation of Animal and Vegetable Sub- 
stances which Contain Nitrogen. — Wheneyer a compound 
containing carbon, hydrogen, and nitrogen is heated in a 
closed vessel, so that the air cannot reach it, and it cannot 
burn up, the nitrogen passes out of the compound, not as 
nitrogen, but partly at least in combination with hydrogen, 
as ammonia. Nearly all animal substances contain car- 
bon, hydrogen, oxygen, and nitrogen, and many of them 
give off ammonia when heated in the way described. 
Heating in this way is called destructive distillation. 
Similarly, compounds containing carbon, oxygen, and 
hydrogen, even though they are thoroughly dry, when 
heated give off oxygen in combination with hydrogen as 
water (see Experiment 1). The coal that is used for 
making illuminating-gas contains some hydrogen and 
nitrogen in chemical combination, and when the coal is 
heated in a closed vessel ammonia is given off. 

Natural Decomposition of Animal and Vegetable Sub- 
stances that Contain Nitrogen. — The decay or slow natural 
decomposition of animal and vegetable substances exposed 
to the air is familiar to every one. It is caused by the 

7T 



72 THE ELEMENTS OF CHEMISTRY, 

action of hosts of minute living things (called bacteria) 
acting together with the oxygen of the air.. Some animal 
substances give off ammonia when they decompose in the 
air. When animal substances decompose under proper 
conditions either a nitrite or a nitrate is formed; the 
former is derived from nitrous acid, H]Sr02, ^^^ latter 
from nitric acid, HNO3. In some countries where the 
conditions are favorable to the process immense quantities 
of nitrates are found, chiefly potassium nitrate or salt- 
petre, KNO3, and sodium nitrate or Chili saltpetre, 
NaNOg, so called because it is found in Chili in large 
quantities. From the nitrates nitric acid can easily be 
obtained. 

How Compounds of Nitrogen are Made. — The principal 
compounds of nitrogen are those which it forms with 
hydrogen and oxygen. They are made either from 
ammonia or from nitric acid by methods which will be 
described. 

Ammonia, NH3. — The conditions under which ammonia 
is formed have been mentioned. The chief sources at 
present are the '^^ammoniacal liquor ^^ of the gas-works, 
which is the water through which the gas has been passed 
for the purpose of removing the ammonia, and refuse 
animal matter. By adding hydrochloric acid to this 
liquid ammonium chloride, commonly called sal ammoniac, 
is formed. This is the most common compound contain- 
ing ammonia, and it is therefore used in the laboratory 
for making ammonia. 

Preparation of Ammonia. 

Experiment 50. — To a little ammonium chloride on a watch- 
glass add a few drops of a strong solution of caustic soda, and 



COMPOUNDS OF NITROGEN IVITH HYDROGEN, ETC, 73 

notice the odor of the gas given off. Do the same thing with 
caustic potash. Mix small quantities of quicklime and ammonium 
chloride in a mortar, and notice the odor. Has ammonium chlo- 
ride this odor ? 

To prepare ammonia mix slaked lime and ammonium 
cliloride in tlie proportion of 2 parts of the former to 
1 part of tlie latter^ and gently heat the mixture. It has 
been shown that besides the ammonia, which is given off 
in the form of gas, calcium chloride, CaLCl2, and water 
are formed in the reaction. It is represented thus: 

2NH,C1 + CaO^H, = 2NH3 + CaCl, + 2H,0. 

Experiment 51. — Arrange an apparatus as shown in Fig. 23, 
omitting, however,- the funnel-tube ; a cork with one hole will 
therefore answer. Weigh 100 grams quicklime into a dish, and 




Fia. 23. 

bring this into the flask. Add just enough water to slake it 
without making it moist, then add 50 grams ammonium chloride 
and mix by shaking. Push the stopper into place and gently heat 
the flask, which should rest upon a sand-bath. After the air is 
driven out, the gas will be completely absorbed by the water in 
the first Woulff's flask. Disconnect at J, and connect with 
another tube bent upward. Collect some of the escaping gas by 



74 



THE ELEMENTS OF CHEMISTRY. 




displacing air, placing the vessel with the mouth doivnward^ as 
the gas is much lighter than air. The arrange- 
ment is shown in Fig. 24. Th6 vessel in which 
the gas is collected should be dry, as water ab- 
sorbs ammonia very readily. Hence also it can- 
not be collected over water. In the gas collected 
introduce a burning stick or taper. Does the 
gas burn ? Does it support combustion ? In 
worlcing with the gas great care must he taken 
to avoid 'breathing it in any quantity. After 
enough has been collected, connect the delivery- 
FiG. 24. tube again with the series of Woulff's flasks, 

and pass the gas over the w^ater as long as it is given off. 

Properties of Ammonia. — Erom the observations made 
in the experiment just performed you see that ammonia 
is a colorless^ transparent gas. It has a very penetrating 
characteristic odor. In concentrated form it causes suffo- 
cation. It is but little more than half as heavy as air. 
It is easily converted into a liquid by pressure and 
cold. When the pressure is removed from the liquefied 
ammonia it passes back to the form of gas. In so doing 
it absorbs heat. These facts are taken advantage of for 
the artificial preparation of ice. Carrels ice-machine is 
used for this purpose. Ammonia does not burn in the 
air, but does burn in oxygen. It is absorbed by water in 
very large quantity. One volume of water at the ordinary 
temperature dissolves about 600 volumes of ammonia-gas^ 
and at 0° C. about 1000 volumes. 

Ammonia-water. — The solution of ammonia in water is 
w^hat we commonly have to deal with under the name 
ammonia. In ordinary language it is sometimes called 
^^ spirits of hartshorn ^^ and also ^'^ household ammonia.^' 
The solution loses all its gas when heated to the boiling 
temperature. 



COMPOUNDS OF NITROGEN IVITH HYDROGEN, ETC, 75 

Nitric Acid, HNO3. — ^^ effect the direct union of 
nitrogen with oxygen and hydrogen is not easier than to 
effect the direct union of nitrogen and hydrogen to form 
ammonia. The silent and continuous action of minute 
organisms in the soil is always tending to transform the 
waste products of animal life into compounds closely 
related to nitric acid. In general, by oxidation the 
nitrogen of animal substances is converted into nitric acid, 
while by reduction it is converted into ammonia. 

Preparation of Nitric Acid. — Nitric acid is obtained 
from a nitrate like potassium nitrate, KNO3, or sodium 
nitrate, NaNOg , by treating with sulphuric acid. 

2NaN03 + H^SO, = Na^SO, + 2HNO3. 

Sodium , sulphuric • sodium , nitric 

nitrate ^"^ acid ^'^® sulphate ^"^ acid. 

You see that the hydrogen of the sulphuric acid changes 
place with the sodium of the nitrate. 

Experiment 52. — Arrange an apparatus as shown ]n Fig. 25. 
In the retort put 25 grams sodium nitrate (Chili saltpetre) and 
15 grams concentrated sulphuric acid. On heating gently, nitric 
acid will distil over and be condensed in the receiver. In the 
latter stage of the operation the vessel becomes filled with a red- 
dish-brown gas. The acid which is collected has a somewhat 
yellowish color. 

Pure Nitric Acid is a colorless liquid. It gives ofE color- 
less fumes when exposed to the air. When boiled it 
undergoes slight decomposition into oxygen, water, and 
compounds of nitrogen and oxygen. One of these com- 
pounds is colored, and it is this which is noticed in the 
last experiment and whenever strong nitric acid is boiled. 
Nitric acid suffers a similar decomposition when exposed 
to the action of the direct rays of the sun. In conse- 



76 THE ELEMENTS OF CHEMISTRY. 

quence of this decomposition bottles contaiuing strong 
nitric acid sometimes contain a reddish-brown gas above 
the liquid after standing for some time. Strong nitric 
acid acts violently on many substances, particularly those 
of animal and vegetable origin, decomposing them. It 




Fig. 2b. 

causes bad wounds in contact with the flesh; it eats 
through clothing; it burns wood; it dissolves metals; and 
it is altogether one of the most active of chemical sub- 
stances. In working with it it is necessary to take the 
greatest care. 

Ordinary or Commercial Nitric Acid contains only about 
68 per cent of the chemical compound HNOg. The rest 
is mostly water, though there are several impurities 
present in small quantities. 

How to Make Strong Nitric Acid.* — Pure, strong nitric 

* The experiments with strong nitric acid may be performed or 
not as tlie teacher thinks best. They had better not be performed 
by the pupils, and should not be performed by any one who is not 
experienced in working with chemical substances. 



COMPOUNDS OF NITROGEN IVITH HYDROGEN, ETC. 77 

acid can be made by mixing commercial nitric acid and 
commercial strong sulphnric acid and distilling. 

Experiment 53. — Mix together 400 grams ordinary concen- 
trated sulphuric acid and 80 grams ordinary concentrated nitric 
acid. Distil the mixture slowly from a retort arranged as in 
Experiment 52, taking care to keep the neck of the retort cool by 
placing filter-paper moistened with cold water on it. Use the 
acid thus obtained for the purpose of studying the properties of 
pure nitric acid. 

Nitric Acid Gives up Oxygen Readily. — Nitric acid is 
much used on account of the ease with which it gives up 
oxygen. Many substances burn up in strong nitric acid. 

Experiment 54. — Pour concentrated nitric acid into a wide test- 
tube, so that it is about one fourth filled. Heat the end of a stick 




Fig. 26. 

of charcoal of about the size of a lead-pencil, and, holding the 
other end with a forceps, introduce the heated end into the acid. 
It will continue to burn with a bright light, even though it be 
placed below the surface of the liquid. The action is oxidation. 
The charcoal in this case finds the oxygen in the acid and not in 
the air. Great care must be taken in performing this experiment. 
The charcoal should not come in contact with the sides of the 



7^ THE ELEMENTS OF CHEMISTRY. 

test-tube. A large beaker-glass should be placed beneath the 
test-tube, so that in case the tube should break, the acid would 
be caught and prevented from doing harm. The arrangement of 
the apparatus is shown in Fig. 26. The gases given off from the 
tube are offensive and poisonous. Hence this as well as all other 
experiments with strong nitric acid should be carried on either 
out of doors or under a hood in which the draught is good. 

Experiment 55. — In a small flask put a few pieces of granulated 
tin. Pour on this just enough strong nitric acid to cover it. 
Heat gently over a small flame. What takes place ? What is the 
appearance of the substance left in the flask ? It is mostly a 
compound of tin and oxygen. (See Experiment 7.) 

Action of Nitric Acid upon Some Metals. — Generally 
when an acid acts upon a metallic element like silver, 
copper, lead, etc., the hydrogen of the acid is liberated 
and the metallic element takes its place. Thus when 
nitric acid acts upon silver the action takes place as repre- 
sented in the equation 

Ag + HNO3 == AgNO, + H. 

Silver and nitric acid give silver nitrate and hydrogen. 

The substances thus formed are called nitrates. At the 
same time the hydrogen and a part of the oxygen are 
taken out of the acid, and compounds of nitrogen and 
oxygen are formed which are represented by the formulas 
NOg, NO, and ^J^. The first of these, nitrogen per- 
oxide, ]Sr02 , is a colored gas, and as some of it is always 
formed when nitric acid acts upon metals in the air, the 
presence of the reddish-brown gas observed in the experi- 
ments already performed with nitric acid will be readily 
understood. 

Experiment 56 — Dissolve a few pieces of copper- foil in ordi- 
nary commercial nitric acid diluted with about half its volume of 
water. The operation should be carried on in a good-sized flask 
and either out of doors or under a good hood. What action takes 



COMPOUNDS OF NITROGEN PVITH HYDROGEN, ETC. 79 

place ? After the action is over what is the appearance of the 
liquid in the flask ? Pour it out and evaporate under a hood to 
crystallization. Compare the substance thus obtained with copper 
nitrate. — Heat specimens of each. — Treat small specimens with 
sulphuric acid. — Do the substances appear to be identical ? "What 
reasons have you for considering them identical ? 

Aqua Regia is made by mixing together . concentrated 
nitric and hydrochloric acid. It is an excellent solvent. 
It is called aqua regia because it dissolves the king of 
metals, gold. Similarly nitric acid is called aquafortis, 
or strong water. In olden times all liquids were regarded 
as kinds of water, and all gases as kinds of air. 

The Oxides of Nitrogen. — Nitrogen combines with oxy- 
gen in five proportions. The names and symbols of the 
compounds formed are here given : 

Nitrous oxide N2O 

Nitric oxide NO or N2O2 

Nitrogen trioxide NaOs 

Nitrogen peroxide NO2 or NaQ* 

Nitrogen pentoxide NaO» 

A Good Illustration of the Lav/ of Multiple Proportions. 

— The combining weight of nitrogen being 14, the above 
symbols represent the fact that in the compounds of 
nitrogen and oxygen the quantities of oxygen combined 
with 28 parts of nitrogen are 16, 32, 48, 64, and 80; or 
16, twice 16, three times 16, four times 16, and five times 
16 parts of oxygen are combined with 28 parts by weight 
of nitrogen. This series of compounds is an excellent 
illustration of the law of multiple proportions, which is 
one of the most important and interesting truths of 
chemistry. — [What is the law of multiple proportions ? 
How does this series illustrate it ?] 



8o THE ELEMENTS OF CHEMISTRY, 

Nitrous Oxide, ISTgO. — This compound is formed by 
reduction of nitric acid when the acid acts upon metals 
under favorable conditions of concentration and tempera- 
ture. It is usually prepared by heating ammonium 
nitrate. The decomposition takes place as represented, 
thus : 

NH,N03 = N,0 + 2H,0 

^mTrTtl"" heated gives ^xTd? and water. ' 

Experiment 57. — In a retort heat 10 to 15 grams crystalHzed 
ammonium nitrate until it has the appearance of boiUng. Do not 
heat higher than is necessary to secure a regular evolution of gas. 
Connect a wide rubber tube directly with the neck of the retort, 
and collect the gas over water, as in the case of oxygen. 

Properties of Nitrous Oxide. — It is colorless and trans- 
parent and has a slightly sweetish taste. When inhaled it 
causes a kind of intoxication, which is apt to show itself 
in the form of hysterical laughing. Hence the gas is 
commonly called laughing-gas. Inhaled in larger quantity 
it causes unconsciousness and insensibility to pain. It is 
therefore used in certain surgical operations, particularly 
in pulling teeth. It supports combustion almost as well 
as pure oxygen. 

Experiment 58. — Insert into it a piece of burning wood, a can- 
dle, and a small piece of phosphorus. 

Nitric Oxide, NO. — This gas, as has been stated, is 
formed when nitric acid acts upon some metals, as copper. 
It seems probable that two changes take place : 

(1) Nitric oxide, water, and copper oxide are formed as 
represented in the equation 

2HNO3 + 3Cu = H,0 + 3CuO + 2N0. 

" and copper .ive water and -ppe^ and ^^^ 



COMPOUNDS OF NITROGEN IVITH HYDROGEN, ETC. 8i 



(2) Then the copper oxide forms copper nitrate with 
some of the acid, and this nitrate dissolves : 



CuO + 2HXO3 



^^PP^^ and 
oxide 



nitric acid 



= Cu(N03), 

give 



HO. 



copper 
nitrate 



and water. 



The complete action is represented by the equation 

8HNO3 + 3Cu = 3Cu(X03), + 4H,0.+ 2X0. 

Experiment 59. — Arrange an apparatus as shown in Fig. 27. 
In the flask put a few pieces of copper-foil. Tl. 
Cover this with water. Xow add slowly, wait- ^~''^ 
ing each time, ordinary concentrated nitric 
acid. When enough acid has been added gas 
will be given off. If the acid is added quickly 
it not infrequently happens that the evolution 
of gas takes place too rapidly, so that the liquid 
is forced out of the flask through the funnel- 
tube. This can be avoided by not being in a 
hurry. What is tlie color of the gas in the flask 
at 9fst ? "Whatsis it after the action has con- 
tinued for a short time ? Fill two or three 
vessels with the gas over water. 

Propertiggs of Nitric Oxide. — Xitric oxide 
is a colorless, transparent gas. Its most 
remarkable property is its power to com- 
bine directly with oxygen when the two are fig. 27. 
brought together. The reaction is represented by the 
equation 

XO + = xo,. 

The product is nitrogen peroxide, and this at ordinary 
temperatures is a reddisli-brown gas. 

Experiment 60. — Turn one of the vessels containing colorless 
nitric oxide with the mouth upward and uncover it. ^hat takes 
place ? Explain the appearance of the colored gas in Experiment 
59, and the fact that it afterward disappeared. What was in the 
vessel at the beginning of the operation ? Do not inhale the gas. 




82 THE ELEMENTS OF CHEMISTRY. 

Perform the experiment with nitric oxide where there is a good 
draught. 

Experiment 61. — Into one of the vessels containing nitric 
oxide insert a burning candle. Does the gas burn ? Does it 
support combustion? 

Nitric oxide does not burn and does not support com- 
bustion. 

Nitrogen Peroxide, NOg. — This is the reddish-brown 
gas formed in the experiments with nitric oxide. It has 
a disagreeable smell and is poisonous. It is used in large 
quantities in the manufacture of the extremely important 
substance sulphuric acid, as will be explained farther on. 



CHAPTER X. 

CHLORINE AND ITS COMPOUNDS WITH HYDROGEN 
AND OXYGEN. 

Introductory. — A little later you will see that oxygen 
and nitrogen are members of families of elements. The 
other members of the oxygen family resemble oxygen in 
many respects, and the other members of the nitrogen 
family resemble nitrogen. Hydrogen, strange to say, does 
not belong to any family but stands by itself. Another 
family is the chlorine family, of which chlorine is the 
best-known member. 

Occurrence of Chlorine. — Chlorine, though widely dis- 
tributed in nature, does not occur in very large quantity 
as compared with oxygen and hydrogen. It is found 
chiefly in combination with the element sodium as common 
salt or sodium chloride, which is represented by the 
symbol NaCl. It is also found in combination with other 
elements, as potassium, magnesium, etc. In small quan- 
tity it occurs in combination with silver, forming a 
valuable ore of silver. All the chlorine with which we 
have to deal is made from common salt. 

Preparation of Chlorine. — The simplest method of pre- 
paring chlorine and the one that is almost exclusively 
used on the large scale consists in passing an electric 

83 



84 THE ELEMENTS OF CHEMISTRY. 

current through a water solution of potassium chloride. 
This causes chlorine to appear at one pole of the battery 
and potassium at the other. The chlorine escapes as 
such, while the potassium acts upon the water, forming 
hydrogen and potassium hydroxide or caustic potash. 
Chlorine is also obtained by the action of an electric cur- 
rent on a solution of zinc chloride and on molten sodium 
chloride. 

In the laboratory chlorine is made by oxidizing hydro- 
chloric acid. Under proper conditions the action repre- 
sented in the following equation takes place: 

2HC1 + = H,0 + 2C1. 

'^^^ac?d^^^^^ and oxygen give water and chlorine. 

Laboratory Method. — In the laboratory it is most con- 
venient to bring together ordinary hydrochloric acid and 
manganese dioxide, Mn02, a substance which you have 
already had to deal with in preparing oxygen. The action 
which takes place is represented thus : 

MnO, + 4HC1 = MnC], + 2H,0 + 2C1. 

Commercial Manufacture of Chlorine. — Chlorine is an 
important article of commerce, as it finds extensive use 
for bleaching and disinfecting. As manganese dioxide is 
a comparatively expensive substance, efforts have been 
made to devise some cheaper method of preparation than 
that just mentioned. Up to recently two methods have 
been extensively used. They are : 

(1) Deacon^ s Process. — This consists in passing air and 
hydrochloric acid together through a heated tube contain- 
ing clay balls which have been saturated with a solution 
of copper sulphate or blue vitriol. Exactly why the 



CHLORINE AND SOME OF ITS COMPOUNDS. 



85 



oxidation should take place under these circumstances is 
not known. The main part of the action is the oxidation 
of the hydrochloric acid, as represented in the above 
equation. 

(2) WekIo7i's Process. — This consists, in the first place, 
in making the chlorine from manganese 
dioxide and hydrochloric acid, and then, 
instead of throwing away the liquid con- 
tained in the vessel, mainly manganese 
chloride, MnCl2 , in solution, this is treated 
with steam, lime, and air, and thus con- 
verted into a substance that acts towards 
hydrochloric acid like manganese dioxide, 
setting chlorine free. 

These methods have been largely sup- 
planted by that referred to in the para- 
graph ^^Preparation of Chlorine. 
process. 




Fig. 28. 

This is the electrolytic 



Experiment 62. — In a flask put about 100 grams (3 to 4 
ounces) of black oxide of manganese. Pour upon it enough 
ordinary concentrated hydrochloric acid to cover it completely. 
Arrange the apparatus as shown in Fig. 28. Heat gently in a 
sand-bath, when chlorine will be given off. Collect six or eight 
d7^2/ cylinders or bottles full of chlorine by letting the delivery- 
tube extend to the bottom of the collecting vessel and covering 
the mouth of the vessel with a piece of paper. You can see when 
the vessel is full by the color of the gas. — The experiments with 
chloriiu should he carried on in a place where the draught is 
good. Do not inhale the gas, 

(1) Into one of the vessels containing chlorine introduce a little 
finely powdered antimony. The two elements combine at once 
with evolution of light and heat. [In what respect does this ex- 
periment resemble the one in which iron was burned in oxygen ?] 

(2) Into a second vessel introduce a few pieces of heated cop- 



S6 THE ELEMENTS OF CHEMISTRY. 

per-foil. Combination takes place with evolution of light and 
heat. A compound of copper and chlorine is formed. 

(3) Into a third vessel introduce a piece of paper with writing 
on it, some flowers, and pieces of colored calico. Most of the 
colors will be destroyed if the substances are moist. 

(4) Into a fourth vessel introduce a dry piece of the same 
colored calico as that used in (3). The dry piece is not bleached; 
the moist piece is. 

Properties of Chlorine. — Chlorine is a greenish-yellow 
gas. It has a disagreeable smell, and acts upon the 
passages of the throat and nose, causing irritation and 
inflammation. The feeling produced is much like that of 
" 2i cold in the head. '^ Inhaled in concentrated form, 
that is, not diluted w^ith a great deal of air, it would cause 
death. It is much heavier than air. Its specific gravity 
is 2.49. A litre of chlorine gas at 0° C. and atmospheric 
pressure weighs 3.22 grams. It is soluble in water and 
acts upon mercury, and therefore must be collected by 
displacement of air. It combines readily with other sub- 
stances and destroys colors or bleaches. It is one of the 
most active elements. In bleaching it decomposes the 
colored substances and forms colorless substances. It is 
used to disinfect substances. 

Disinfection. — Substances given off from persons sick 
with some diseases, such as typhoid fever, smallpox, etc., 
are apt to cause the same diseases in well persons. It is 
therefore desirable to destroy them. This is called dis- 
infecting. One of the most valuable substances for this 
purpose is chlorine. It is sold in the form of " bleaching- 
powder,^^ known also as ^^ chloride of lime," which is a 
compound made by passing chlorine gas into slaked lime. 
A solution of this substance m w^ter is a Yalua,ble dis- 



I 



CHLORINE AND SOME OF ITS COMPOUNDS. 87 

infectant. Old drains, sinks, etc., from which bad odors 
arise may be freed from their odors and rendered harmless 
by adding enough of such a solution. 

Combination of Hydrogen and Chlorine. — Just as hy- 
drogen burns in the air it burns also in chlorine. 

Experiment 63. — Light a jet of hydrogen in the air and care- 
fully introduce it into a vessel containing chlorine. Does it con- 
tinue to burn ? What is the appearance of the flame ? What 
evidence have you that a product is formed ? Test the gas remain- 
ing in the jar with blue litmus solution shaken up in it, and com- 
pare with the action of chlorine gas on the solution. 

The burning of hydrogen in air or oxygen is, as you 
have seen, the act of combination of hydrogen and 
oxygen, the product being water in the state of vapor, and 
therefore invisible. When hydrogen burns in chlorine the 
action consists in the union of the two gases, the product 
being hydrochloric acid, HCl, which forms clouds in the 
air. In both cases the action is accompanied by heat and 
light. 

Chlorides. — Just as the compounds of oxygen with other 
elements are called oxides, so the compounds of chlorine 
with the elements are called chlorides. 

Hydrochloric Acid, HCl. — The only compound which 
chlorine and hydrogen form with each other is hydro- 
chloric acid. It has already been shown that hydrogen 
burns in chlorine, and that hydrochloric acid is formed. 
The two gases may be mixed together and allowed to 
stand together indefinitely in the dark, and no action will 
take place. If, however, the mixture is put in a room 
lighted by the sun, but where the sun does not shine 
directly upon it, combination takes place gradually; and 
if the sun i^ allowed to shine upon the mixture for an 



SS THE ELEMENTS OF CHEMISTRY, 

instant, explosion occurs, and this is the sign of the com- 
bination of the two gases. The same sudden combination 
is effected by applying a flame or spark to the mixture. 
In this case light causes chemical action. The art of 
photography depends upon the fact that light has the 
power to cause chemical changes, as will be more fully 
explained later. It should be specially noted that the 
cause of the chemical changes in the cases referred to is 
not the heat but the light. If the substances are heated 
to the same temperature in the dark, the changes do not 
take place. 

Preparation of Hydrochloric Acid. 

Experiment 64. — Pour 2 or 3 c.c. concentrated sulphuric acid 
on a gram or two of common salt in a test-tube. What takes 
place ? Is a gas given off ? What is its appearance ? 

Hydrochloric acid is always made by treating common 

salt with sulphuric acid, when the reaction takes place 

which is represented in the equation 

2NaCl + H^SO, = Na^SO, + 2HC]. 

Sodium ^„, sulphuric -^^ sodium ^^ . hydrochloric 
chloride ^^^ acid ^^^® sulphate ^"^ acid. 

The products are sodium sulphate and hydrochloric acid. 

The hydrochloric acid is given off as a gas, and the sodium 

sulphate remains behind in the flask. 

Experiment 65. — Arrange an apparatus as shown in Fig. 23, 
page 73. Weigh out, separately, 100 grams common salt, 100 
grams concentrated sulphuric acid, and 20 c.c. water. Mix the 
acid and water, taking the usual precautions (see note p. 51). 
Let the mixture cool down to the ordinary temperature, and 
then pour it on the salt in the flask. Now heat the flask gently, 
and the gas will be regularly given off. Conduct it at first 
over water contained in two or three Woulff's bottles until what 
passes over is completely absorbed in the first Woulff's bottle. 
When the air has been displaced, the gas is all absorbed as soon as 



CHLORINE AND SOME OF ITS COMPOUNDS. 89 

it comes in contact with the water. — After the gas has passed for 
ten to fifteen minutes disconnect at A (see Fig. 23). Notice the 
fumes. These become denser by "blowing the breath '' upon 
them. Apply a lighted match to the end of the tube. Does the 
gas burn ? Collect some of the gas in a dry cylinder by displace- 
ment of air, as in the case of chlorine. The specific gravity of 
the gas being 1.26, the vessel must of course be placed with the 
mouth upward. Has the gas any color ? Is it transparent ? 
Insert a burning stick or candle in the cylinder filled with the 
gis. Does the gas support combustion ? — Connect the generating- 
fl isk again with the bottles containing water, and let the process 
c )ntinue until no more gas comes over. The reaction repre- 
sented in the equation 

2NaCl + H2SO4 = ]SraaS04 + 2HC1 

is now complete. After the flask has cooled dowm pour water on 
the contents, and when the substance is dissolved filter it and 
evaporate to such a concentration that, on cooling, the sodium 
sulphate is deposited. Pour off the liquid, and dry the solid sub- 
stance by placing it upon folds of filter-paper. Compare the sub- 
stance with the common salt which you put in the flask before 
the experiment. What proofs have you that the two substances 
a:"e not the same? Heat a small piece of each in a dry tube 
closed at one end. What differences do you notice ? — Treat a 
small piece of each in a test-tube with a little concentrated sul- 
phuric acid. What difference do you notice ? — If in the experi- 
ment you should recover all the sodium sulphate formed, how 
much would you have ? [The combining weight of sodium is 23 ; 
of sulphur, 32; and of chlorine 35.5.] The relations between the 
quantities of the substances that take part in the reaction are 
expressed as follows: 

2NaCl + H2SO4 = ^2iS0, 

2(23 -f 35.5) 2xl-f32 + 4xl6 2x23 + 32+4x16 



117 parts + 98 parts = 142 parts 

+ 2HC1. 

2(1 + 35.5). 



+ 73 parts. 

The quantity of sodium sulphate formed is to the quantity of 
sodium chloride as 142 is to 117. Therefore if you use 100 grams 



90 THE ELEMENTS OF CHEMISTRY, 

of sodium chloride, the quantity of sodium sulphate formed is 
found by solving the simple proportion: 

117 : 100 :: 142 : grams of sodium sulphate. 

— Put about 50 c.c. of the liquid from the first Woulflf's bottle 
in a porcelain evaporating-dish. Heat over a small flame just to 
boiling. Is hydrochloric acid given off? Can all the liquid be 
driven off by boiling ? — Try the action of the solution on some 
iron filings. Is a gas given off ? What is it ? — Add some to a 
little granulated zinc in a test-tube ? Is hydrogen given off ? — 
Add some to a little manganese dioxide in a test-tube. Is chlo- 
rine given off ? — Add ten or twelve drops of the acid to 2 or 3 
c.c. water in a test-tube. Taste the dilute solution. How would 
you describe the taste ? — Add a drop or two of a solution of blue 
litmus, or put into it a piece of paper colored blue w-ith litmus. 
Litmus is a vegetable color prepared for use as a dye. Other 
vegetable colors are changed by hydrochloric acid. — The color will 
be restored by adding a few drops of caustic soda or ammonia. 

Composition of Hydrochloric Acid. — That hydrochloric 
acid consists of hydrogen and chlorine is shown by the 
fact that it is formed when hydrogen combines with 
chlorine. It has further been shown that when the two 
gases combine they do so in equal volnmes^ 1 volume of 
hydrogen combining with 1 volume of chlorine ; and these 
2 volumes form 2 volumes of hydrochloric-acid gas. In 
36.5 parts by weight of hydrochloric-acid gas there are 
contained 1 part by weight of hydrogen and 35.5 parts by 
weight of chlorine. The combining weight of chlorine 
being 35.5, the composition of hydrochloric-acid gas is 
represented by the symbol HCl. 

Chemical Conduct of Hydrochloric Acid. — 1. Hydro- 
chloric acid gives up its hydrogen when brought in contact 
with certain substances like iron, zinc, etc., which belong 
to the class called metals; and it takes up these metallic 



CHLORINE AND SOME OF ITS COMPOUNDS. 9^ 

elements in place of the hydrogen. Thus zinc and 
hydrochloric acid give zinc chloride and hydrogen: 

Zn + 2liCl = ZnCl, + 2H. 

2. In contact with substances which give up oxygen, 
or with oxygen itself under certain circumstances, it gives 
up its chlorine, while the hydrogen combines with oxygen 
to form water : 

2HC1 + rrz H,0 + 2C1. 

3. When it acts upon metallic oxides or compounds of 
the metals with oxygen, such as magnesia or magnesium 
oxide, MgO; lime or calcium oxide, CaO; zinc oxide, 
ZnO, etc., — compounds which do not easily give up their 
oxygen, — the hydrogen of the acid combines with the 
oxygen of the oxide to form water, while the metals com- 
bine with the chlorine : 

MgO + 2HC1 = MgCl, + H,0; 
CaO + 2HC1 = CaCl, + H,0; 
ZnO + 2HC1 = ZnCl', + H,0. 

Compounds of Chlorine with Oxygen and with Hydrogen 
and Oxygen. — As you have seen, chlorine combines very 
readily with hydrogen, and hydrogen with oxygen, and 
the products are stable compounds. On the other hand, 
chlorine does not combine directly with oxygen. In- 
directly the two elements can be made to combine, but 
the compounds decompose very easily into the elements. 

Compounds of Chlorine with Hydrogen and Oxygen. — 
The principal reaction made use of for the preparation of 
compounds of chlorine, oxygen, and hydrogen consists in 
treating caustic potash or potassium hydroxide, KOH, 



92 THE ELEMENTS OE CHEMISTRY. 

with chlorine. If the sohition of caustic potash is warm 
and concentrated the reaction takes place inainly as repre- 
sented in this equation : 

6K0H + 6C1 nr 5KC1 + KCIO3 + 3H,0. 

The compound KCl is potassium cliloride; KCIO3 is the 
well-known substance potassium chlorate, or chlorate of 
potash, used for making oxygen in Experiments 20 and 
21. 

If the solution is dilute the reaction takes place thus : 

2K0H + 2C1 = KCl + KCIO + 11,0. 

The product KCIO is known 2i% potassium hypochlorite. 

Hypochlorous Acid, IICIO, and Chloric Acid, HClOg. — 
Just as sodium nitrate, NaNOg, yields nitric acid, IINO3, 
when treated with sulphuric acid (see Experiment 52); 
and sodium chloride, NaCl, yields hydrochloric acid, HCl 
(see Experiment 65); so potassium chlorate, KCIO3, 
yields chloric acid, HCIO3; and potassium hypochlorite, 
KCIO, yields hypochlorous acid, HCIO : 

2NaN03 + H^SO, = 2HNO3 + Na^SO,; 
2NaCl + H^SO, = 2HC1 + Na^SO,; 
2KCIO3 + H^SO, =: 2HCIO3 + K^SO,; 
2KC10 + H^SO, = 2HC10 + K^SO,. 

Bleaching-poiuder, or '^ chloride of lime,^' is a substance 
similar to potassium hypochlorite, and is formed by pass- 
ing chlorine into slaked lime. Ifc will be more fully con- 
sidered under Calcium. 

Other Compounds of Chlorine, Hydrogen, and Oxygen. — 
There are four compounds of chlorine, hydrogen, and 
oxygen. As far as composition is concerned, they bear a 



CHLORINE AND SOME OF ITS COMPOUNDS. 93 

simple relation to one another. Beginning with hydro- 
chloric acidp we have a series of compounds the successive 
members of which differ by one combining weight of 
oxygen : 

Hydrochloric acid HCl. 

Hypochlorous acid HCIO. 

Chlorous acid HClOa- 

Chloric acid. HCIO3 

Perchloric acid HCIO4. 

This series, like the series of compounds of nitrogen 

and oxygen, illustrates very clearly the Jaiu of vmltij^le 

proportions. [What is the law of multiple proportions ? 

In what way does this series illustrate the law ?] 



CHAPTER XL 
ACIDS-BASES-XEUTRALIZATION— SALTS. 

Introduction. — You have already met with a number of 
substances called acids. It is now time to inquire what 
these substances have in common that lead chemists to 
call them all acids. TThat is there in common, for exam- 
ple, between the heavy, oily liquid sulphuric acid and the 
colorless gas hydrochloric acid ? It is not possible to 
understand the nature of their common properties without 
reference to a class of substances to which special atten- 
tion will be called in due time. These are the allcalies, 
which are the most marked members of a class of sub- 
stances known as lases. Acids and bases have the power 
to destroy the characteristic ]3roperties of each other. 
When an acid is brought in contact with a base in proper 
proportions, the characteristic properties of both the acid 
and the base are destroyed. They are said to neutralize 
each other. 

A Study of Neutralization. — The most common acids 
are sulphuric, hydrochloric, and nitric acids. Among the 
more common bases are caustic soda, caustic potash, and 
lime. A convenient way to recognize whether a substance 
has acid or basic properties is by means of certain color- 
changes. The dye litmus is blue. If a solution that is 
colored blue with litmus is treated with a drop or two of 
an acid, the color is changed to red. If now the red 

94 



ACIDS— BASES— NEUTRALIZA TION—SAL TS. 



95 



solution is treated with a foAV drops of a solution of a 
base, the blue color is restored. There are many other 
substances which change markedly in color, according to 
whether the solutions in which they are present are acid 
or basic. An infusion of red cabbage, for example, 
changes color when treated with an acid, and recovers its 
color when treated with an alkali. 

Experiment 66.— Make dilute solutions of nitric, hydrochloric, 
and sulphuric acids (4 c.c. dilute acid, such as is used in the lab- 
oratory, to about 200 c.c. of water), and of caustic soda or 
caustic potash (about 1 gram to 200 c.c. of water). Measure off 
a definite quantity, say 20 c.c, of each of the acid solutions. Add 
a few drops of a solution of blue 
litmus. Gradually add to each of 
the measured quantities of acid 
sufficient dilute caustic soda to cause 
the red color just to change to blue. 
As long as the solution is red it 
is acid. When it turns blue it is 
alkaline. At the turning-point it is 
neutral. The experiment is best 
performed with the aid of a burette, 
which is a graduated tube with an 
opening from which small quanti- 
ties can be poured. A convenient 
shape is that represented in Fig. 29. 
At the lower end is a small opening. 
The flow of the liquid from the 
burette is controlled by means of a 
small pinch- cock. It will require 
some practice to enable you to 
know exactly when the red color 
disappears and the blue appears, 
but with practice the point can be 
recognized with accuracy. Should 

too much alkali be allowed to get 

Fig 29 
into the acid, add a small measured 

quantity of the acid from another burette. In one experiment 




9^' THE ELEMENTS OF CHEMISTRY, 

neutralize 20 c.c. of the acid; in a second 10 c.c; in a third 
15 c.c. — What relation do the quantities of alkali used bear to 
one another ? — Does it always require a definite quantity of alkali 
to neutralize a certain quantity of acid ? 

What is Formed when an Acid Neutralizes a Base ? — 

To determine this we may use in larger quantities the 
same substances as those used in the preceding experi- 
ments. 

Experiment 67. — (1) Dissolve 10 grams caustic soda in 100 c.c. 
water. Add hydrochloric acid slowly, examining the solution 
from time to time by means of a piece of paper colored blue 
with litmus. As long as the solution is alkaline it will cause no 
change in the color of the paper. The instant it passes the point 
of neutralization it changes the color of the paper red. When 
this point is reached, evaporate the water on a water-bath to com- 
plete dryness, and see what is left. — Taste the substance. Has it 
an acid taste ? Does it suggest any familiar substance? If it is 
common salt or sodium chloride, how ought it to conduct itself 
when treated wath concentrated sulphuric acid ? Does it conduct 
itself in this way ? Is the substance an alkali ? Is it an acid ? 
Is it neutral ? Its formation took place according to the equation 

HCl + NaOH = NaCl + H2O. 

2. Perform the same experiment, using nitric acid instead of 
hydrochloric acid. — Compare the product with sodium nitrate. 
Heat a small specimen of each in a tube closed at one end. What 
takes place ? Heat a small specimen of each with a little con- 
centrated sulphuric acid in test-tubes. What takes place ? The 
reaction between nitric acid and caustic soda is represented thus : 

HNO3 + NaOH = NaNOs + H^O. 

3 Similarly, sulphuric acid and caustic soda give sodium sul- 
phate and water, thus : 

H2SO. + 2NaOH = Na2S04 + 2H2O. 

4. Similar reactions take place with caustic potash. Hydro- 
chloric acid and caustic potash yield potassium chloride and water: 

HCl + KOH = KCl + H,0. 



ACIDS— BASES— NEUTRALIZATION— SALTS. 97 

Nitric acid and caustic potash yield potassium nitrate and water ; 

HNO3 + KOH = KNO3 + H.,0. 
Sulphuric acid and caustic potash yield potassium sulphate and 
water : 

H2SO4 + 2K0H = K2SO4 + 2H2O. 

What these Experiments Show. — Considering the facts 
just learned, you see 

(1) That an acid contains hydrogen; 

(2) That a base contains a metal ; 

(3) That when an acid acts upon a base the hydrogen 
and the metal exchange places; 

(4) That the substance obtained from the acid by 
replacing the hydrogen by a metal is neutral; 

(5) That the substance formed by replacing the metal 
of the baso by hydrogen is water. 

The Fourth Statement not General. — All these state- 
ments except the fourth are true of all cases. In some 
cases after substituting a metallic element for the 
hydrogen of an acid, the substance has an alkaline .reac- 
tion; and in other cases the product has an acid reaction. 

Products Formed when a Metal Acts upon an Acid. — 
You have already seen that hydrochloric acid and sul- 
phuric acid act upon certain metals, as iron and zinc, and 
that the action consists in giving up hydrogen and taking 
up metal in its place. The products of this action are 
the same in character as those formed by the action of 
acids on bases. 

Acids, Bases, and Salts. — An acid is a substance contain- 
ing hydrogen, which it easily exchanges for a metal when 
treated with a metal itself, or with a compound of a metal 
called a base. 

A hase is a substance containing a metal combined with 



98 THE ELEMENTS OF CHEMISTRY, 

hydrogen and oxygen. It easily exchanges its metal for 
hydrogen when treated with an acid. 

The products of the action of an acid on a base are, 
first, water, and, second, a neutral substance called a salt. 
In the examples already given, sodium chloride, potassium 
chloride, sodium nitrate, potassium nitrate, sodium sul- 
phate, and potassium sulphate are salts. 

What is a Metal? — Unfortunately it is not an easy 
thing to give a satisfactory answer to this question. We 
can give examples of metals, such as iron, zinc, silver, 
calcium, magnesium, etc. ; but when we attempt to dis- 
cover the common properties of these substances we are 
somewhat at a loss. In general, any element which has 
the power to enter into an acid in the place of the 
hydrogen is called a metal. With hydrogen and oxygen 
a metal forms a product which has the power to neutralize 
acids; that is to say, which has basic properties. 

Importance of Water in the Experiments on Neutraliza- 
tion. — One fact of great importance is not taken into 
account in what has thus far been said about neutraliza- 
tion. It is thus: The substances must he brought together 
in solution. Dry hydrochloric acid and dry sodium 
hydroxide, for example, do not act upon each other, and 
the same is true of other perfectly dry acids and bases. 
The water is essential to the actio7i. This raises the ques- 
tion: 

What is Solution ? — No satisfactory answer can yet be 
given to this question. There are many liquids besides 
water in which solids can be dissolved, but for the present 
attention may be confined to solutions in water. Of these 
there are two kinds: 



/iCIDS— BASES-NEUTRALIZATION— SAL TS. 99 

(1) The solutions of some substances have the power to 
conduct electricity; 

(3) The solutions of other substances Jiave not this 
power. 

Substances of the first class are called electrolytes. To 
this class belong acids, bases, and salts. 

Substances of the second class are called non-electrolytes. 
To this class belong sugar and many other substances less 
familiar. 

There is good reason for believing that, when an elec- 
trolyte is dissolved in water, a part of the substance is 
broken down or dissociated into simpler parts called ions. 
Thus, hydrochloric acid is believed to break down to a 
greater or less extent into the ions H and CI; nitric acid 
into the ions H and NO,, etc. So also, sodium hydroxide 
is believed to break down into the ions ISTa and OH; 
potassium hydroxide into the ions K and OH. Further, 
sodium chloride is believed to break down into the ions 
Na and 01; potassium nitrate into the ions K and NO3, 
etc. 

The extent of this breaking down or dissociation (called 
electrolytic dissociation) is determined largely by the 
dilution — the greater the dilution the greater the dissocia- 
tion. 

Ions not the Same as Atoms, — The ions that are believed 
to be present in the solutions of electrolytes are not to be 
confounded with the atoms or with definite compounds. 
The atoms (see Atomic Theory) of which the smallest 
particle of hydrochloric acid is believed to be made up 
are, to be sure, hydrogen and chlorine. The ions into 
>7hich the molecule of hydrochloric acid breaks down or 

L.ofC. 



lOO THE ELEMENTS OF CHEMISTRY. 

dissociates when dissolved in water are these atoms highly 
chargea with electricity. When the electricity is dis- 
charged the elements appear in their ordinary forms. 

Definition of Acids and Bases in Terms of the Theory of 
Electrolytic Dissociation. — If the views above presented 
are correct, and the evidence upon which they rest is 
undoubtedly strong, then acids and bases should be 
defined as follows : 

(1) An acid is a substance that gives hydrogen ions 
when dissolved in water. * 

(2) A base is a substance that gives ions of the composi- 
tion represented by the formula OH, called hydroxyly 
when dissolved in water. 

The common properties of acids — the sour taste, the 
evolution of hydrogen when brought together with metals, 
their action on dyes, their power to neutralize bases — are 
believed to be due to the fact that they all give hydrogen 
ions. 

So also tlie common properties of bases — their alkaline 
taste, their action on dyes, their power to neutralize acids 
— are believed to be due to the fact that they give hydroxyl 
ions. 

Products of Neutralization. — In the light of the above 
ideas what conception are we to form of the act of neutral- 
ization ? When, for example, hydrochloric acid and 
sodium hydroxide are brought together in solution what 
' are the changes ? Hydrochloric acid gives the ions H and 
01; sodium hydroxide gives the ions Na and OH. So 
that at first the water solution contains the ions 
H + 01 + Na + OH. 

* Some other solvents act like water, but not in so marked a way. 



j4CIDS— BASES— NEUTR^ LIZA T ION— SAL TS. I o I 

But water has not the power to dissociate water; and if 
the constituents of water, the ions H and OH, find them- 
selves together, they unite to form water. We should, 
therefore, have 

H + CI + Na + HO r= CI + Na + H,0. 

The characteristic hydrogen ion of the acid and the char- 
acteristic hydroxyl ion of the base would thus be removed 
and a condition of neutrality would result. The ions CI 
and Na would remain uncombined unless the solution 
were concentrated. By evaporating off the water they 
would come more and more into combination, and with the 
disappearance of the water they would wholly disappear 
as such, and in their place we should have the compound 
sodium chloride. 

Names of Acids.— The termination ic is generally used 
in naming acids, as is seen in the names hydrochloric, 
sulphuric, nitric, etc. If a second acid containing the 
same elements exists and the proportion of oxygen con- 
tained in it is smaller than in the acid the name of which 
ends in ic^ the second acid is given a name ending in otis. 
Thus, chlorous acid, HCIO2 , contains a smaller proportion 
of oxygen than chloric acid, HCIO3. 

When more than two acids containing the same ele- 
ments are known, prefixes are used to distinguish them. 
In the series of chlorine acids already referred to (see page 
93) there is one acid which, so far as the proportion of 
oxygen contained in it is concerned, stands below chlorous 
acid. It is called hypochloTous acid, the prefix hypo being 
derived from a Greek word meaning under. Further, 
there is an acid which contains a larger proportion of 



I02 THE ELEMENTS OF CHEMISTRY. 

oxygen than chloric acid. It is called jt?erchloric acid, the 
Latin prefix j^j^r meaning here very or fully. It will be 
seen that the names of the acids vary with the proportion 
of oxygen contained in them. 

Names of Bases. — As already stated, a base is a com- 
pound of a metal with hydrogen and oxygen or hydroxyl, 
HO. Thus caustic soda has the formula NaOH, caustic 
potash KOH, lime Ca(0H)2, etc. They are commonly 
known as hydroxides. To distinguish between the hy- 
droxides of the different metals, the names of the metals 
are put before the name hydroxide. Thus, caustic soda, 
NaOH, is called sodium hydroxide; caustic potash, KOH, 
is called potassium hydroxide; slaked lime, Ca(OH)j, is 
called calcium hydroxide, etc. These compounds are 
called hydrates by some chemists. 

Names of Salts. — The salts derived from a given acid 
receive a general name, and this general name is quali- 
fied in each case by the name of the metal contained 
in the salt. Thus, all the salts derived from nitric 
acid are called nitrates; all those derived from chloric 
acid are called chlorates; those derived from sulphuric 
acid are called sulphates. So too, further, the salts of 
chlorous acid are called chlorites; those of nitrous acid, 
nitrites; those of sulphurous acid, sulphites; etc., etc. 
You will notice that the last syllable of the name of 
the salt differs according to the name of the acid. If 
the name of the acid ends in ic, the name of the salt 
ends in ate. If the name of the acid ends in ous, the 
name of the salt ends in ite. To distinguish between 
the different salts of the same acid, the name of the metal 
contained in it is put before the general name of the salt. 



/iCIDS— BASES— NEUTRALIZA TION—SAL TS. 103 

Thus, the potassmm salt of nitric acid is called potassium 
nitrate, the sodium salt is called sodium nitrate; the 
calcium salt of sulphuric acid is called calcium sulphate; 
the magnesium salt of nitrous acid is magnesium nitrite; 
the calcium salt of hypochlorous acid is calcium hypo- 
chlorite, etc., etc. 

[Give the name and formula of the potassium salt of 
perchloric acid. — Give the name and formula of the 
sodium salt of hypochlorous acid. — Give the name and 
formula of the sodium salt of nitric acid. ] 

Salts of Hydrochloric Acid. — If the salts of hydrochloric 
acid were named in accordance with the principle just 
explained, they would be called liydrochlorates. But these 
salts are identical with the products formed by direct 
combination of the metals with chlorine. Thus hydro- 
chloric acid and zinc act as represented in the equation 

Zn + 2HCl=:ZnCl2 + 2H; 

while zinc and chlorine act thus : 

Zn + 201 = ZnCl,. 

In each case the same product, ZnCl2 , is formed. But 
these compounds of metals with chlorine are called chlo- 
rides, as has already been explained. Hence the name 
hydrochlorates is unnecessary. 

Acid Properties and Oxygen. — The observation that 
oxygen is generally present in acids led at one time to 
the belief that it is a necessary part of these substances. 
Hence the name oxygen, which means the acid-former, 
was given to it. That oxygen is not essential to the exist- 
ence of acid properties is shown in the case of hydrochloric 



I04 THE ELEMENTS OF CHEMISTRY. 

acid, and in a few other similar cases. It must be said, 
however, that the acid properties of substances are 
generally due to the presence of oxygen. Some substances 
with basic properties are converted into acids by causing 
them to combine with more oxygen. 



I 



CHAPTER XII. 
CARBON. 

Carbon Found in All Living Things. — Wood, meat, 
fruits, and most other products of vegetable or animal 
life, when heated to a sufficiently high temperature 
Uachen, and afterwards, if they are heated in the air, they 
burn up, as we say. This blackening is due to the fact 
that the substances all contain carbon. When they are 
heated without access of air the other elements are first 
driven off in various forms of combination, while a part 
of the carbon remains behind. If they are heated in 
the air, the carbon finally combines with oxygen to form 
a colorless gas — it burns up. 

Destructive Distillation. — The process of heating sub- 
stances in closed vesels and collecting the prducts formed 
is called destructive distillation. Among the most inter- 
esting examples of destructive distillation are those of coal 
and of wood. Coal is heated, as already stated under 
Ammonia, for the purpose of making illuminating-gas. 
Wood is heated for the purpose of making charcoal. 
Many interesting and important sulistances are obtained 
in these processes. Some of them will be taken up 
farther on. 

105 



io6 THE ELEMENTS OF CHEMISTRY. 

Occurrence of Carbon. — From what lias already been 
said you will see that the principal form in which carbon 
occurs in nature is in combination with other elements. 
It occurs not only in all living things, but in their fossil 
remains, as in coal. Coal-oil or petroleum consists of a 
large number of compounds that contain only carbon and 
hydrogen. Most j)roducts of plant-life contain the ele- 
ments carbon, hydrogen, and oxygen. Among the more 
common of these products are sugar, starch, cellulose, 
etc. Most products of animal life contain carbon, hy- 
drogen, oxygen, and nitrogen. Among them may be 
mentioned albumin, fibrin, casein, etc. Carbon occurs in 
the atmosphere in the form of carbon dioxide or carbonic 
acid. It also occurs in the form of salts of carbonic acid, 
the carbonates, which are widely distributed, forming 
some large mountain-ranges. Limestone, marble, and 
chalk are calcium carbonate. 

Forms of the Element Carbon. — ITncombined, the ele- 
ment occurs 23ure in two very different forms in nature : 
(1) As diamond; and (2) 2S> grapliite ox pluiiibago. 

Diamond. — The celebrated diamond-beds are in the East 
Indies, Borneo, Sumatra, Brazil, and South Africa. 
When found, diamonds are covered with an opaque layer, 
which must be removed before the beautiful properties 
aj)pear. Diamond is the hardest substance known. 
Heated to a high temperature in oxygen, it burns up, 
forming only carbon dioxide. 

Small diamonds have been made by dissolving charcoal 
in molten iron in a crucible in an electric furnace, and 
then plunging the crucible into water. Under these con- 
ditions the outside of the molten mass is quickly solidi- 



CARBON. 107 

fied while the inner portions are still liquid and under 
strong pressure. Small diamonds have been found in 
meteorites. 

Graphite. — Graphite, or plumbago, is found in nature 
in large quantities. It can be prepared artificially by dis- 
solving charcoal in molten iron. From this solution it is 
deposited as graphite on cooling. It has a grayish-black 
color and a metallic lustre. It is quite soft, leaving a 
leaden-gray mark on paper when drawn across it, and is 
hence used in the manufacture of so-called lead pencils. 
It is also used as a lubricant for bicycle chains, etc. It is 
sometimes called Hack lead. Heated to a very high tem- 
perature in the air, or in oxygen, it burns up, forming 
only carbon dioxide. 

Amorphous Carbon. — All forms of carbon which are not 
diamond, nor graphite, are included under the name 
amorphous carhon. This name means simply that it is 
not crystallized. 

How Charcoal is Made. — Charcoal is that form of carbon 
which is made by the cliarring process. This consists in 
heating without a free supply of air. The substance 
almost exclusively used in the manufacture of charcoal is 
wood. Wood consists of a large number of substances, 
nearly all of which are made up of the three elements 
carbon, hydrogen, and oxygen. When wood is burned in 
the air the products are carbon dioxide and water. If the 
air is prevented from coming freely in contact with the 
wood^ the hydrogen is given off partly as water and partly 
in the form of volatile compounds containing carbon and 
oxygen. The carbon, however, is mainly left behind as 
charcoal, as there is not enough oxygen present to burn it. 



io8 THE ELEMENTS OF CHEMISTRY. 

A Charcoal-kiln. — This consists essentially of a pile of 
wood so arranged as to leave spaces between the pieces. 
The pile is then covered either with brick-work or some 
rough material through which the air will not pass easily, 
as, for example, a mixture of powdered charcoal, turf, and 
earth. Small openings are left in the covering. A part 
of the wood burns and furnishes heat enough to char the 
rest. After a time the holes through which the air gains 
access to the wood are closed up, and the process stops. 
Charcoal, which is impure amorphous carbon, is left behind. 

Properties of Charcoal. — Ordinary charcoal is a black, 
comparatively soft substance. It burns in the air, though 
not easily, unless the gases which are formed are con- 
stantly removed and fresh air is supplied, as by blowing 
with a bellows. It burns readily in oxygen, as we have 
seen (Experiment 24). The product of the combustion 
in oxygen and in air, when there is no lack of oxygen, is 
carbon dioxide, CO2. In the air when the draught is bad, 
another compound of carbon and oxygen, carbon mon- 
oxide, CO, is formed. 

Coke. — This is a form of amorphous carbon which is 
made by heating ordinary gas-coal without access of air, 
as is done on a large scale in the manufacture of illumi- 
nating-gas. Coke bears to coal about the same relation 
that charcoal bears to wood. 

Lamp-black is a very finely divided form of carbon 
which is deposited on cool objects placed in the flames of 
burning oils. Most flames used for illuminating purposes 
give a black deposit of soot on objects placed in them. 
This soot is largely made up of fine particles of carbon. 
It is used in the manufacture of printer^s ink. Carbon is 



. CARBON. 109 

acted upon directly by very few substances, and is insolu- 
ble, so that it is impossible to destroy the color of printer^s 
ink without destroyi]:ig the material upon which it is 
impressed. 

Bone-black, or Animal Charcoal, is a form of amorphous 
carbon which is made by charring bones and other animal 
substances. Unless it is treated with an acid it contains 
the incombustible substances which form a part of bones. 

Charcoal-filters. — Bone-black and wood-charcoal are 
very porous and have the power to absorb gases. When 
plaeed in air containing bad-smelling gases, these are 
absorbed and the air thus purified. When water which 
contains disagreeable substances is treated with charcoal, 
these are wholly or partly absorbed and the water im- 
proved. Charcoal-filters are therefore extensively used. 
A charcoal-filter to be of value should be of good size, and 
from time to time the charcoal should be taken out and 
renewed. The small filters which are screwed into faucets 
are of little value, as the charcoal soon becomes charged 
with objectionable matter and thus becomes a source of 
contamination. 

Bone-black Filters. — Some coloring matters are removed 
from liquids by passing the liquids through bone-black 
filters. On the large scale, this fact is taken advantage 
of in the refining of sugar. The solution of sugar first 
obtained from the cane or beet is strongly colored; and if 
it were evaporated, the sugar deposited from it would be 
dark-colored. If, however, the solution be first passed 
through bone-black filters, the color is removed. 

Experiment 68. — Make a filter of bone-black by fitting a paper 
filter into a funnel 12 to 15 mm. (5 to 6 inches) in diameter at its 



no THE ELEMENTS OF CHEMISTRY, 

mouth. Half fill this with bone-black. Pour a dilute solution 
of indigo * through the filter. If the conditions are right the 
solution will pass through colorless. — Do the same thing with ink 
much diluted with w^ater. — If the color is not completely removed 
by one filtering, filter the solutions again. — The color may also be 
removed from solutions by putting some bone-black into them 
and boiling for a time. Try this with half a litre each of the ink 
and indigo solutions used in the first part of the experiment. 
Use about 4 to 5 grams bone-black in each case. Shake the solu- 
tions frequently while heating. 

Charring Prevents Decay. — Cliarcoal does not decay in 
the air or under water nearly as readily as wood. That is 
another way of stating the chemical fact that the sub- 
stances of which wood is made up are more susceptible to 
ordinary chemical action than charcoal is. We have one 
illustration of this in the relative ease with which charcoal 
and wood burn in the air. Piles w^hich are driven below 
the surface of water are charred to protect them from the 
action of those substances which cause decay. 

Coal. — Under this head are included a great many kinds 
of impure amorphous carbon which occur ready-formed in 
nature. Ordinarily coals are divided into hard and soft 
coals^ or anthracite and hituminous coals. Then there are 
substances more closely related to wood^ and therefore 
called lignite, and those which represent a very early stage 
in the process of coal-formation, viz. , jjeat. 

Formation of Coal. — A close examination of all those 
varieties has shown that they have been formed by the 
gradual decomposition of vegetable material where there 
was not free access of air. The process has been going on 
for ages. Sometimes the substances have been subjected 

* Prepared by treating powdered indigo for some time with warm 
concentrated sulphuric acid and diluting with much water. 



CARBON. 1 1 1 

to great pressure, as can be seen from the position in 
which they occur in the earth. 

Destructive Distillation of Coal. — All forms of coal con- 
tain other substances besides carbon. The soft coals are 
particularly rich in other substances. When heated they 
give off a mixture of gases and vapors of volatile liquids. 
The gases are, for the most part, useful for illuminating 
purposes. The liquids form a black, tarry mass known 
as coal-tar, from which are obtained many valuable com- 
pounds of carbon. The gases are passed through water 
for the purpose of removing certain impurities. This 
water absorbs ammonia and forms the ammoniacal liquor 
of the gas-works. 

'Diamond, Graphite, and Charcoal Different Forms of the 
Element Carbon. — An element, as you have learned, is a 
form of matter which cannot be decomposed into simpler 
substances by any means now known to chemists. From 
hydrogen we can get nothing but hydrogen, except by 
bringing it together with some other element; from 
nitrogen we can get nothing but nitrogen, etc. In the 
case of carbon, however, it is possible for the element to 
appear in three forms, which differ markedly from one 
another. That they are the same substance, chemically 
speaking, can be proved by a comparatively simple experi- 
ment. If we were to burn the same weight of diamond, 
of graphite, and of charcoal, and collect and weigh the 
carbon dioxide formed in each case, we should find that 
the weight of carbon dioxide formed is the same in each 
case. Further, knowing the composition of carbon 
dioxide, we know how much carbon is contained in a given 
weight of the gas. Calculating the quantity of carbon 



ri2 THE ELEMENTS OF CHEMISTRY. 

contained in the carbon dioxide obtained in burning a 
piece of diamond., we should find that it is exactly equal 
to the weight of the diamond; and the same thing is true 
of graphite and charcoal. 

Problem. — How much carbon dioxide, CO2 , should be ob- 
tained by burning 0.5 gram diamond ? The combining weight of 
carbon is 12. 

Common Properties of the Different Forms of Carbon. — 

Notwithstanding the marked differences in their appear- 
ance the difEerent forms of carbon have some properties 
in common. They are insoluble in all ordinary liquids.* 
They are tasteless, inodorous, and infusible. When 
heated without access of air, they remain unchanged 
unless the temperature is very high. 

Allotropy. — That one and the same substance can 
appear in markedly different forms under different condi- 
tions is seen in the case of water. Hail and snow would 
hardly be suspected of being the same substance by one 
not quite familiar with them. The difference in this 
case, as in that of carbon, is believed to be due to the way 
in which the' small particles of which the substances are 
made up are arranged. If we had a number of small 
pieces of wood all of the same size and shape, say cubes, 
and should carefully arrange them in some regular way, 
we might easily make a comparatively compact mass of 
them, and the mass would have a regular form. We 
might, further, arrange them in some second way with 
regularity. And we might simply throw the pieces 
together in a jumble. These three kinds of arrangement 
would represent, in a rough way, the difference between 

* They are all soluble in molten iron. 



CARBON. , 113 

the three forms of carbon. Each pile would be made of 
wood, but in outward appearance they would differ from 
one another. In a similar way oxygen and ozone differ 
from each other. The power which some elements have 
of existing in different conditions is called allotropy. 

Chemical Conduct of Carbon. — At ordinary temperatures 
carbon is an inactive element. If it is left in contact 
with any one of the elements thus far treated of — viz., 
hydrogen, oxygen, chlorine, and nitrogen — no change 
takes place. At higher temperatures, however, it readily 
combines with other elements, especially oxygen. It 
combines with oxygen either directly, as when it burns in 
the air or oxygen; or it abstracts oxygen from some of 
the oxides. 

Direct Combination of Carbon with Oxygen. — This has 
already been illustrated in Experiment 24, and is familiar 
to every one in charcoal-fires. That carbon dioxide is the 
product formed may be shown by passing the gas into 
lime-water, when insoluble calcium carbonate • will be 
thrown down. Lime-water is made by adding water to 
some quicklime. The lime is slaked and some of the 
product, calcium hydroxide, Ca(0H)2, dissolves in the 
water. The excess of the calcium hydroxide settles and 
leaves a clear solution above if the vessel is allowed to 
stand quietly. 

Experiment 69. — Put a small piece of charcoal in a piece of 
hard-glass tube. Pass oxygen through the tube, at the same 
time heating it. Pass the gases into clear lime-water. Arrange 
the apparatus as shown in Fig. 30. A is a bottle containing 
oxygen ; B is the hard-glass tube containing the charcoal ; C is 
the cylinder with clear lime-water. The reason why lime-water 
is used is that an insoluble compound is formed, and this can be 



114 



THE ELEMENTS OF CHEMISTRY. 



seen, and it can be separated from the liquid and examined. 
The reaction which takes place is represented thus : 
CaOaH, + CO2 = CaCOa + H2O. 



Lime 



carbon 



calcium 



-'•dioxide gi- caX;^e-d water. 

(insoluble) 




Fig. 30. 

No other common gas acts in this way with lime-water. Hence, 
when, under ordinary circumstances, a gas is passed into lime- 
water and an insoluble substance is formed, we may conclude 
that the gas is carbon dioxide. 

Carbon Abstracts Oxygen from Oxides. — This may be 
illustrated by the following experiments: 

Experiment 70.— Mix together 2 or 3 grams powdered copper 
oxide, CuO, and an equal bulk of powdered charcoal ; heat in a 
hard-glass tube to which is fitted an out- 
let tube, as shown in Fig. 31. Pass the 
gas which is given off into clear lime- 
water contained in a test-tube. — Is it car- 
bon dioxide ? What evidence have you 
that oxygen has been extracted from the 
copper oxide ? What is the appearance 
of the substance left in the tube ? Does 
it suggest the metal copper ? Treat a 
little with strong nitric acid. What 
^^°' ^^' should take place if the substance is 

metallic copper ? (See Experiment 56.) What does take place? 




CARBON. 115 

The reaction between the charcoal and the copper oxide is repre- 
sented thus: 

20uO + C =2Ca + CO2. 

Experiment 71. — Perform a similar experiment with a little 
wliite arsenic in a small glass tube closed at one end. Take 
about equal parts of charcoal and arsenic. White arsenic is a 
compound of the elements arsenic and oxygen, AS2O3. The re- 
action which takes place when it is heated with charcoal is repre- 
sented thus : 

2AS2O3 + 30 == 4As + 3C0,. 

The element arsenic is volatile, and is hence driven out of the 
bottom of the tube and deposited on the sides of the tube above 
the mixture in the form of a mirror with a metallic lustre. 

Use of Carbon (Charcoal) as a Reducing Agent. — As has 
already been explained, the abstraction of oxygen from a 
componnd is called reduction. Hence carbon is called a 
reducing agent. It is extensively nsed for the purpose of 
extracting metals from their ores, which are the forms in 
which they occur in nature. Thus, iron does not occur 
in nature as iron, but in combination with other elements, 
particularly oxygen. In order to get the metal the ore 
must be reduced, or, in other words, the oxygen must be 
extracted. This is always accomplished by heating it 
with some form of carbon, either charcoal or coke. 

[What other element which you have already studied 
acts as a reducing agent ? Give an example of its reducing 
power.] 



CHAPTEK XIII. 

COMPOUNDS OF CARBON WITH HYDROGEN, 
OXYGEN, AND WITH NITROGEN. 

Compounds of Carbon and Hydrogen. — In the laboratory 
it is not a simple matter to effect combination between 
carbon and hydrogen except in a few simple cases. In 
nature processes are in operation that give rise to the 
formation of a large number of compounds containing 
these elements; and, further, in the manufacture of 
illuminating-gas from coal the conditions are such as to 
cause the combination of carbon and hydrogen, several 
interesting compounds being thus formed. There are no 
other two elements that combine with each other in as 
many different proportions as carbon and hydrogen. The 
compounds thus formed are known as hydrocarhons. The 
nuraber of hydrocarbons known is very great, being some- 
where near two hundred. Fortunately, investigation has 
shown that quite simple relations exist between these 
compounds; and hence, though the number is large, the 
study is not as difficult as might be expected. 

Petroleum, which is a mixture of various hydrocarbons, 
gaseous, liquid, and solid, is found in many places in the 
earth in large quantity, particularly in Pennsylvania, West 
Virginia, Ohio, California, Texas, and the Caucasus. 

Ii6 



COMPOUNDS OF CARBON JVITH HYDROGEN, ETC, n? 

When it is brought into the air, the pressure being 
removed, the gases are given off. There are several 
gaseous hydrocarbons given off, and a large number of 
liquids left behind. 

Refining Petroleum. — The vapors from petroleum when 
mixed with air are explosive, and the thicker liquids clog 
the lamps and wicks. Therefore these must be removed 
before the oil is fit for household use. This is done by 
(1) distilling, (2) washing with sulphuric acid, (3) washing 
with alkali, and (4) washing with water. The product 
thus prepared is called Jcerosene, 

In refining petroleum a number of products are obtained 
which cannot be used in lamps. Those which are lighter 
than kerosene, that is to say those which boil at a lower 
temperature, are known as gasoline^ naphtha^ lenzine^ etc. 
From the heavier portions, or those which boil at higher 
temperatures than kerosene, liihricating oils and paraffin 
are made. Each of these substances is a mixture of 
several hydrocarbons. 

Hydrocarbons contained in Petroleum. — The simplest 
hydrocarbon contained in petroleum is methane, or marsh- 
gas, CH^; the next has the composition C^Hg, the next 
Cgllg , etc. It will be seen that these compounds bear a 
simple relation to one another, as far as composition is 
concerned. They are the first members of a series the 
names and symbols of the first eight members of which 
are given below : 

CH^, Methane, or Marsh-gas; 

C^Hg, Ethane; 

CgHg, Propane; 

O^Hj^,, Butane; 



Ii8 THE ELEMENTS OF CHEMISTRY. 

C5HJ2, Pentane; 
CgHj^, Hexane; 
C^H^g, Heptane; 
CgHjg, Octane. 

Homology.- — The first member of the series differs from 
the second by CH2; there is also this same difference, in 
general, between any two consecutive members of the 
series. This relation is known as liomology, and such a 
series as an homologous series. Carbon is distinguished 
from. all other elements by its power to form homologous 
series. 

The Ethylene Series of Hydrocarbons. — ^Besides the 

series above mentioned w^hich is known as the marsh-gas 

series, there are other homologous series of hydrocarbons. 

There is one beginning with ethylene, ^211^, examples of 

which are 

Ethylene, C^H,; 

Propylene, C3H,; 

Butylene, O^Hg. 

The Acetylene Series. — There is a series beginning with 
acetylene, examples of which are 

Acetylene, C2H2; 
Allylene, C3H,. 

The Benzene Series. — Another series begins with ben- 
zene, CgHg. Some of the members of this series are 

Benzene, CgHg; 
Toluene, C^Hg; 
Xylene, CgH,,. 

Marsh-gas, Methane, Fire-damp, CH^. — Marsh-gas is 
found in nature in petroleum, and is given off when the 



COMPOUNDS OF CARBON JVITH HYDROGEN, ETC. 119 

oil is taken out of the earth. It also occurs in ^^ natural 
gas/'' It is formed, as the name implies, in marshes, as 
the product of a reducing process. Vegetable matter is 
composed of carbon, hydrogen, and oxygen. When it 
undergoes decomposition in the air in a free supply of 
oxygen, the final products are carbon dioxide and water. 
When the decomposition takes place without access of 
oxygen, as under water, marsh-gas, which is a reduction 
product, is formed. It bears to carbon much the same 
relation that ammonia bears to nitrogen. 

Occurrence of Marsh-gas in Coal-mines. — Marsh-gas is 
met Avith in coal-mines, and is known to the miners as 
fii^e-damp. Mixed with air it is one of the causes of the 
terrible explosions which occur in coal-mines. 

Preparation of Marsh-gas. — Marsh-gas is most readily 
prepared in the laboratory by heating sodium acetate with 
caustic potash and quicklime. 

Experiment 72. — -Mix 5 grams dry sodium acetate, 5 grams 
potassium hydroxide, and 1\ grams quicklime. Heat in a retort. 
Collect over water as iu making nitrous oxide. Does the gas 
burn ? Does it give light in burning ? 

Properties of Marsh-gas. — Marsh-gas is a colorless, 
transparent, tasteless, inodorous gas slightly soluble in 
water. It burns, forming carbon dioxide and water. 
When mixed with air, the mixture explodes if a flame or 
spark comes in contact with it. 

Ethylene, Olefiant Gas, CJI^. — This hydrocarbon is 
formed by heating a mixture of ordinary alcohol and con- 
centrated sulphuric acid. It is a colorless gas which can 
be condensed to a liquid. It burns with a luminous flame. 

Acetylene, C2II2. — Acetylene is formed when a current 



I20 



THE ELEMENTS OF CHEMISTRY, 



of hydrogen is passed between carbon poles which are 
incandescent in consequence of the passage of a pow^erful 
electric current. In this case carbon and hydrogen com- 
bine directly. It is formed also when the flame of an 
ordinary laboratory burner (Bunsen burner) ^^ strikes 
back/^ or burns at the base without a free supply of air. 
It is most easily formed by treating calcium carMde (which 
see) with water when the reaction below represented takes 
place : 



CaC, + 2H,0 = 

Calcium 
carbide 



and water 



give 



acety- 
lene 



+ Ca(OH), 

, calcium 

^"^ hydroxide. 



Experiment 73. — Arrange an apparatus as shown in Fig. 32. 
This is a small Woulff's flask into one neck of 
which is fitted a funnel-tube furnished with a 
stop-cock, while into the other is fitted a bent 
. glass tube ending in a small opening, or better, 
Jj an acetylene burner. Put a few pieces of 
granulated calcium carbide in the dry flask. 
Now close it and admit water slowly through 
the funnel-tube. After the gas has escaped 
for some time light it. 




Fig. 3^> 



Its odor is unpleasant. It burns with 
a luminous, smoky flame. The gas is 
now much used for illuminating purposes. Bather un- 
satisfactory small bicycle lamps, in which the gas is 
generated from calcium carbide, have been devised. 

The Manufacture of Illuminating-gas. — " Coal-gas/' as 
the name implies, is made from coal. For this pur- 
pose, as has been stated, the coal is heated in closed 
vessels. The products formed are flrst passed through. 
a series of tubes that are kept cooL In these a thick 



COMPOUNDS OF CARBON IVITH HYDROGEN, ETC. 121 

black liquid, known as coal tar, collects. Then the 
gaseous products are passed through water which takes 
up ammonia. The gases which remain are treated with 
two or three other substances to remove impurities, and 
are then collected in large vessels called gasometers. One 
ton of gas-coal yields an average of 10,000 cubic feet 
of gas. 

Coal Tar. — Coal tar contains a very large number of 
compounds, some of which are obtained from it by distil- 
lation. The first products that pass over contain the 
hydrocarbons of the benzene series, of which benzene 
itself is the principal one. 

Carbon Dioxide, CO2. — The principal compound of car- 
bon and oxygen is carbon dioxide, CO2, commonly called 
carbonic acid gas. 

Occurrence of Carbon Dioxide. — Under the head of The 
Atmosphere it was stated that this gas is always present 
in the air. It issues from the earth in many places, par- 
ticularly in the neighborhood of volcanoes. Many mineral 
waters contain it in considerable quantity, as the waters of 
Pyrmont, Selters, and the Geyser Spring at Saratoga. In 
small quantity it is present in all natural waters. In com- 
bination with bases it occurs in enormous quantities, 
particularly in the form of calcium carbonate, CaCOg, 
varieties of which are ordinary limestone, chalk, marble, 
and calc-spar. 

Natural Formation of Carbon Dioxide. — Carbon di- 
oxide is constantly formed in a number of natural 
processes. Thus, all animals in breathing give off carbon 
dioxide. 

Experiment 74. — Blow through some lime-water by means of 



122 



THE ELEMENTS OE CHEMISTRY, 




Fig. 33. 



an apparatus arranged as shown in Fig. 83. What evidence have 
you that your lungs give off carbon dioxide ? 

It has already been shown 
that carbon dioxide is formed in 
the combustion of charcoal and 
wood. In a similar way it can 
be shown that the gas is formed 
whenever any of our ordinary 
combustible materials are burned. 
From our fires as from our lungs, 
and from the lungs of all animals, 
then, carbon dioxide is constantly 
given oflE. Further, the natural 
processes of decay of both vegetable and animal matter 
tend to convert the carbon of this matter into carbon 
dioxide, and this is then spread through the air. The 
process of alcoholic fermentation, and some other like 
processes, also give rise to the formation of carbon dioxide. 
In all fruit-juices there is contained sugar. When the 
fruits ripen, fall off, and decay, the sugar is changed to 
alcohol and carbon dioxide. 

Preparation of Carbon Dioxide. — The easiest way to get 
carbon dioxide is to add an acid to a carbonate. When- 
ever any acid is added to any carbonate there is an evolu- 
tion of gas. 

Experiment 75. — In different test-tubes containing a little 
sodium carbonate add dilute hydrochloric, sulphuric, nitric, and 
acetic acids. — What takes place ? Is a gas given off ? Pass it 
through lime-water. Is it carbon dioxide ? — Perform the same 
experiment with small pieces of marble. What gas is given off ? 

To prepare carbon dioxide in the laboratory, calcium 

carbonate in the form of marble, or limestone, and hydro- 



COMPOUNDS OF CARBON 1VITH HYDROGEN, ETC. 123 



chloric acid are commonly used. The reaction is repre- 
sented thus: 



CaC03 + 2HC1 

Calcium 
carbonate. 



CaCl, + CO, + H,0. 




Fig. 34. 



[What is the substance CaCl,?] 

Experiment 76. — Arrange an apparatus as shown in Fig. 34. 
In the flask put some pieces of marble, and pour 
ordinary hydrochloric acid on it. Collect the 
gas by displacement of air, placing the vessel 
with the mouth upward. Fill several cylinders 
or bottles with the gas. — Into one introduce a 
lighted candle, and afterwards a burning stick. 
What takes place ? With another proceed as if 
pouring water from it. Pour the invisible gas 
upon the flame of a burning candle. Pour some 
of the gas from one vessel to another, and show 
that it has been transferred. Balance a beaker 
on a good-sized scales, and pour carbon dioxide 
into it. If the balance is at all sensitive, the pan 
in which the beaker is placed will go down. 

Properties of Carbon Dioxide. — From the observations 
you have just made you have learned that carbon dioxide 
is a colorless gas at the ordinary temperature; that it is 
incombustible and does not support combustion; and that 
it is heavier than the air. When subjected to a low tem- 
perature and high pressure it is converted into a liquid, 
and this can further be changed to a solid. It has a 
slightly acid taste and smell. 

Why Carbon Dioxide does not Burn. — It does not burn 
for the same reason that water does not ; because in the 
form of the dioxide the carbon already holds in combina- 
tion all the oxygen it has the power to combine with. 
Before it can burn again the carbon dioxide must first be 
decomposed. 



124 THE ELEMENTS OF CHEMISTRY. 

Carbon can do Chemical Work. — Carbon has the power 

to combine with oxygen, and in so doing a definite quan- 
tity of heat is given ofE. A pound of carbon represents 
a definite quantity of chemical energy, which we can get, 
first, in the form of heat, and then convert into other 
forms, as electricity, motion, etc. After the pound of 
carbon has been burned, the product no longer represents 
the energy the carbon did. Similarly, a body of water 
elevated ten or fifteen feet represents a certain quantity of 
energy which can be obtained by allowing the water to fall 
upon the paddles of a water-wheel connected with the 
machinery of a mill. After the water has fallen, however, 
it no longer has the power to do work, or it has no energy. 
In order that it may again do work it must again be lifted 
up. 

Soda-water. — Carbon dioxide dissolves in water, one 
volume of water dissolving about its own volume of the 
gas at the ordinary temperature. When the pressure is 
increased the water dissolves more gas; and when the 
pressure is removed the gas again escaj)es. The so-called 
'' soda-water ^^ is water charged with carbon dioxide under 
pressure. The escape of the gas, when the water is 
drawn, is familiar to every one. The carbon dioxide used 
in charging the water was formerly made from a sodium 
salt of carbonic acid known as ^*' bicarbonate of soda.^^ 

Breathing. — It has been stated that carbon dioxide is 
given off from the lungs as it is from a fire, and the fact 
was shown by means of a simjDle experiment. It is a 
waste product of the processes going on in the animal 
body. Just as it cannot support combustion, so animals 
cannot breathe in it. It is not poisonous any more than 



COMPOUNDS OF CARBON IVITH HYDROGEN, ETC. 125 

water is; but it cannot supply the oxygen which is needed 
for breathing purposes. In it animals die of suffocation, 
as they do in water. Any considerable increase in the 
quantity of carbon dioxide in the air above that which is 
generally present is objectionable, because it decreases the 
proportion of oxygen in the air which is breathed. If 
pure carbon dioxide is introduced into the air it has been 
shown that as much as 5 per cent may be present without 
causing injury to those who breathe it. 

Air in Badly Ventilated Rooms. — In a badly ventilated 
room in which a number of people are collected and lights 
are burning, it is well known that in a short time the air 
becomes foul, and bad effects, such as headache, drowsi- 
ness, etc. , are felt by those in the room. These effects are 
caused, not by the carbon dioxide, but by other waste 
products which are given off from the lungs in the process 
of breathing. The gases given off from the lungs consist 
of nitrogen^ oxygen, carbon dioxide, and water-vapor. 
Besides these, however, there are many substances in a 
fine state of division which contain carbon, and are in a 
state of decomposition. These are poisonous, and appear 
to be the chief cause of the bad effects experienced in 
breathing air which has become contaminated by the 
exhalations from the lungs. 

Carbon Dioxide in Old Wells. — As carbon dioxide is 
formed in the earth wherever an acid solution comes in 
contact with a carbonate, the gas is frequently given off 
from fissures in the earth. As acid solutions are formed 
by the action of the air and moisture upon various 
mineral substances found in and upon the earth, the 
gas is sometimes found in old wells which have not 



126 THE ELEMENTS OF CHEMISTRY. 

been in use for some time, and deaths have been caused 
by descending these wells for the purpose of repairing 
them. It is a good plan to let down a lighted candle into 
such a well before venturing to go down. If the candle 
continues to burn, the air can be breathed without danger. 

Choke-damp. — Carbon dioxide is also met with in mines, 
and is called choice-damp by the miners. The miners know 
that after an explosion caused by fire-damp there is danger 
of death from choke-damp. The reason is this. When 
fire-damp, or marsh-gas, explodes with air the carbon is 
converted into choke-damp, or carbon dioxide, and the 
hydrogen into water. 

Carbon Dioxide the Food of Plants. — Plants live largely 
on the carbon dioxide contained in the air. They have 
the power, with the aid of the sun^s light, to decompose the 
gas, and they then build up the complex compounds of 
carbon which form their tissues, using for this purpose 
the carbon of the carbon dioxide which they have decom- 
posed and returning the oxygen at least partly to the air. 

Plants the Food of Animals. — Animals eat either the 
products of plant-life or other animals which get their 
food from the vegetable kingdom. The food of animals 
comes, then, either directly or indirectly from plants. 
The food taken into the animal body is partly changed 
into other substances which form the structure of the 
animal; and partly it is oxidized, thus serving to keep the 
temperature of the body up to the necessary point. That 
part of the food which suffers oxidation in the body acts 
the same as fuel in a stove. It is burned up, producing 
heat, the carbon being converted into carbon dioxide 
which is given off from the lungs. 



COMPOUNDS OF CARBON JVITH HYDROGEN, ETC 127 

Carbon Dioxide Returns to the Air. — From fires and 
living things carbon dioxide is returned to the air, where 
it again serves as fopd for plants. When the life-process 
stops in the animal or plant, decomposition begins; and 
the final result of this, under ordinary circumstances, is 
the conversion of the carbon into the dioxide. 

No Life Without the Sun. — Every living thing is 
dependent upon the decomposition of carbon dioxide by 
plants, and this decomposition cannot be effected without 
the aid of the sun. If the sun should stop shining, soon 
all life would cease. As the heat of the sun acting upon 
the great bodies of water and on the air gives rise to the 
movements of water which are essential to the existence of 
the world as it is, so the action of the sun^s rays on carbon 
dioxide, in the presence of the delicate and inexplicable 
mechanism of the leaf of the plant, gives rise to those 
changes in the forms of combination of the element carbon 
which accompany the wonderful process of life. 

Carbonic Acid. — A solution of carbonic acid in water 
has a slightly acid reaction. The solution will act upon 
basic solutions and form salts. The composition of the 
sodium salt formed in this way is Na^COg; that of the 
potassium salt K2CO3, etc. These salts are plainly derived 
from an acid, H2CO3, which is carbonic acid. It is prob- 
able that the acid is contained in the solution of carbon 
dioxide in water. It is, however, so unstable that it 
breaks up into carbon dioxide and water : 

H,C03 = CO2 + H,0. 

The Carbonates. — When carbon dioxide acts upon a base 
it forms a salt. Thus, when potassium hydroxide or 



128 THE ELEMENTS OF CHEMISTRY. 

calcium hydroxide is used, the action which takes place is 
represented thus : 

2K0H + C0, = K,C034-H,0; 
Ca(OH), + CO, = CaCOg + H,0. 

Experiment 77. — Pass carbon dioxide into a solution of caustic 
potash until it will absorb no more. Add acid to some of the 
solution thus obtained, and convince yourself that the gas given 
off is carbon dioxide. Write the equations expressing the re- 
actions which take place on passing the carbon dioxide into the 
caustic-potash solution, and on adding an acid to the solution. 
What evidence have you that the gas given off is carbon dioxide ? 

Experiment 78. — Pass carbon dioxide into 50 to 100 c.c. clear 
lime-water. Filter off the white insoluble substance. Try the 
action of a little acid on it. What evidence have you that it is 
calcium carbonate ? How could you easily distinguish between 
lime-water and a solution of caustic potash ? 

Calcium Carbonate Dissolves in Water containing Car- 
bon Dioxide. — If you continue to pass carbon dioxide into 
lime-water after the calcium carbonate has been formed^ 
the carbonate dissolves, and the solution finally becomes 
clear. If this solution is heated, the carbon dioxide is 
driven off and the calcium carbonate is again thrown down. 

Experiment 79. — Pass carbon dioxide first through a little 
water to wash it, and then into 50 to 100 c.c. clear lime-water. 
After the solution has become clear, heat it. 

Hard Water. — Natural waters that flow over limestone 
take up more or less calcium carbonate by virtue of the 
carbon dioxide which they absorb from the air. Such 
waters, which are called ''hard waters," are in the condi- 
tion of the solution of calcium carbonate above referred 
to. "When heated, the calcium carbonate is deposited. 
This is frequently noticed in the deposits in boilers and 
other vessels in which water is boiled. This kind of 



COMPOUNDS OF CARBON IVITH HYDROGEN, ETC, 129 

hardness is called '^temporary hardness/^ to distinguish it 
from ^'permanent hardness^' which is not affected by 
boiling. 

Carbon Monoxide, CO. — This compound is formed when 
a substance containing carbon is burned in an insufficient 
supply of air, — as, for example, when the draught in a 
furnace is not strong enough to remove the products of 
combustion and supply fresh air. It can also be made by 
extracting oxygen from carbon dioxide. It is only neces- 
sary to pass the dioxide over heated carbon, when the 
reaction w^hich is represented in the following equation 

takes place : 

CO, + C = 2C0. 

Formation of Carbon Monoxide in Coal-fires. — The 

formation of carbon monoxide can be well observed in a 
hard-coal fire in an open grate. The air has free access 
to the coal, and at the surface complete oxidation takes 
place. But that part of the carbon dioxide which is 
formed at the lower part of the grate is drawn up through 
the heated coal and is partly reduced to carbon monoxide. 
When the monoxide escapes from the upper part of the 
grate it again combines wdth oxygen, or burns, causing 
the characteristic blue flame always noticed above a mass 
of burning hard coal. 

Carbon Monoxide contained in Water-gas. — Water-gas, 
as has been stated under Hydrogen, is made by passing 
water-vapor over highly heated coal, when this reaction 

takes place: 

C + H,0 = CO + 2H. 

The gas obtained is therefore a mixture of carbon mon- 
oxide and hydrogen. Before use it is enriched by the 



I30 THE ELEMENTS OF CHEMISTRY, 

addition of hydrocarbons from petroleum. As carbon 
monoxide is poisonous, laws have been, passed in some 
States prohibiting the use of water-gas. 

Preparation of Carbon Monoxide. — Carbon monoxide is 
most easily made by heating oxalic acid, C2H20^ with 
sulphuric acid. The change which takes place is repre- 
sented thus: 

C,H,0, = CO, + CO + H,0. 

Sulphuric acid, as will be shown later, has a marked 
power of combining with water. In this case it takes the 
elements of water from the oxalic acid and that which is 
left, C2O3 , breaks down into carbon monoxide and carbon 
dioxide. 

In. order to separate the two gases the mixture is passed 
through a solution of caustic soda, which takes up the 
carbon dioxide [forming what ?j and allows the monoxide 
to pass. 

Experiment 80. — Put 10 grams crystallized oxaHc acid and 
50-60 grams concentrated sulphuric acid in an appropriate-sized 
flask. Connect with two Woulff's flasks containing a solution of 
caustic soda. Heat the contents of the flask gently. Collect 
some of the gas over water. Set fire to the same, and notice the 
characteristic blue flame. 

Properties of Carbon Monoxide. — It is a colorless, taste- 
less, inodorous gas, insoluble in water. It burns with a 
pale blue flame, forming carbon dioxide. It is exceedingly 
"poisonous. Hence it is very important that it should not 
be allowed to escape into rooms occupied by human beings. 

Danger of Coal-stoves. — We sometimes hear of deaths 
caused by the gases from coal-stoyes. The most dangerous 
gas giyen off from coal-stoves is probably carbon niQU' 



COMPOUNDS OF CARBON IVITH HYDROGEN, ETC, 131 

oxide. A pan of smouldering charcoal gives oflE this gas, 
and the poisonous character of the gas is well known. 

Carbon Monoxide a Reducing Agent. — At high tempera- 
tures carbon monoxide combines readily with oxygen and 
it is hence a good reducing agent. In the reduction of 
iron from its ores the carbon monoxide formed in the 
blast-furnace plays an important part. 

Experiment 81. — Pass carbon monoxide over some heated 
copper oxide contained in a bard glass tube. Is the oxide re- 
duced ? How do you know ? Is carbon dioxide formed ? What 
evidence have you ? Was the carbon monoxide free of carbon 
dioxide ? If not, what evidence have you that carbon dioxide is 
formed in this experiment ? 

Illumination. — In all ordinary forms of illumination we 
are dependent upon flames for the light. Whether we use 
illuminating-gas, a lamp, or a candle, the light comes 
from a flame. In the first case, the gas is burned directly ; 
in the case of the lamp, the oil is first drawn up the wick, 
then converted into a gas, and this burns; while, finally, 
in the case of the candle, the solid material of the candle 
is first melted, then drawn up the wick, converted into 
gas, and the gas burns, forming the flame. In each case 
we have, then, a burning gas, and this burning gas we call 
a flame. 

When Burning Gases are Cooled Down they are Extin- 
guished. — You have already learned that substances need 
to be raised to the kindling temperature, before they will 
burn. This statement is as true of gases as of other sub- 
stances. When a current of hydrogen is allowed to escape 
into the air, or into oxygen, no action takes place unless 
it is heated up to the burning temperature, when it takes. 



132 



THE ELEMENTS OF CHEMISTRY, 



fire and continues to burn. If the gas is cooled below this 
temperature^, the flame is extinguished. 

Experiment 82. — Light a Bunsen burner. Bring down upon 
the flame a piece of brass or iron-wire gauze. There is no flame 
above the gauze. That the gas passes through unburned can be 
shown by applying a light just above the outlet of the burner and 
above the gauze. The gas will take fire and burn. By passing 
through the thin ware gauze, then, the gas is cooled down below 
its burning temperature. Turn on a Buusen burner. Do not 
light the gas. Hold a piece of wire gauze about one and a half to 
two inches above the outlet. Apply a lighted match above the 
gauze, when the gas will burn above the gauze, but not below it. 

The Safety-lamp. — The facts illustrated in the last 
experiments are utilized in the miner^'s safety-lamp. One 
of the dangers which the miner has to 
encounter is the occurrence of fire-damp, 
or methane^ CH^ , which w^ith air forms an 
explosive mixture. The explosion can only 
be brought about by contact of a flame 
with the mixture. In order to avoid the 
contact^ the flame of the safety-lamp is 
surrounded by wdre gauze, as show^n in 
Fig. 35. When a lamp of this kind is 
brought into a mixture of marsh-gas and 
air^ it, of course, passes through the wire 
gauze and comes in contact with the flame. 
A small explosion occurs inside the gauze, 
but the flame inside cannot pass through. Hence no 
serious explosion takes place. The flickering of the flame, 
and the occurrence of small explosions inside the gauze, 
furnish the miner with the information th^t he is in 
danger, 




Fig. 35. 



COMPOUNDS OF CARBON IVITH HYDROGEN, ETC, I33 

Causes of the Luminosity of Flames. — There are several 
causes that cause flames to give light. One is the presence 
of solid substances in the flame. If a piece of platinum 
wire is put in a hydrogen flame which gives practically no 
light the flame becomes luminous. This fact has also 
been shown by introducing a piece of lime into the hot, 
non-luminous flame of the oxyhydrogen blow-pipe. A 
similar cause makes ordinary gas-flames luminous. There 
are always present in these flames particles of unburned 
carbon, as is shown by putting a solid substance into the 
flames, when a layer of soot, which consists mainly of 
finely divided carbon, is deposited on it. Again, the 
denser the gas the more light it gives. A candle on the 
top of a high mountain, as Mont Blanc, on which the 
experiment was performed, gives less light than the same 
candle does at the level of the sea. It has lately been 
shown that the formation and decomposition of acetylene 
(which see) in flames is an important factor in the lumi- 
nosity of flames. 

Cyanogen, C^^, — Carbon does not combine with nitro- 
gen under ordinary circumstances. If, however, they are 
brought together at very high temperatures in the presence 
of metals, they combine to form compounds known as 
cyanides. When refuse animal substances, such as blood, 
horns, claws, hair, wool, etc., are heated together with 
potassium carbonate and iron, a substance knejfh as 
potassium ferrocya7iide^ or yelloiu priissiate of potash, 
K^FeCgNg + 3H2O is formed. When this is heated it de- 
composes, yielding potassium cyanide, KCX. From the 
potassium compound it is not difficult to make mercury 



> 



134 THE ELEMENTS OF CHEMISTRY. 

cyanide^ Hg(CN)2. By heating mercury cyanide it breaks 
down^ yielding mercury and cyanogen gas : • 

Hg(CN), = Hg + 0,N,. 

[What analogy is there between thi^ reaction and that 
which takes place when mercury oxide is heated ?] 

Properties. — Cyanogen is a colorless gas, easily soluble 
in water and alcohol. It is extremely poisonous. 

Hydrocyanic Acid, Prussic Acid, HCN. — This acid 
occurs in nature, in combination with other substances, 
in bitter almonds, the leaves of cherry, laurel, etc. It is 
prepared from potassium cyanide, just as hydrochloric acid 
is prepared from sodium chloride. The reaction is repre- 
sented thus : 

2KCN + H,SO, = K,SO, + 2HCN. 

Properties. — Hydrocyanic acid is a volatile liquid. It 
has a very characteristic odor resembling that of bitter 
almonds. It is extremely poisonous. It dissolves in 
water in all proportions, and it is such a solution which is 
known as prussic acid. 

Other Compounds of Carbon. — That part of Chemistry 
which has to do with the compounds of carbon is com- 
monly called Organic Chemistry. It is more convenient 
to deal with this subject after the chemistry of the other 
common elements has been studied. The last part of this 
book will treat of some of the more common and better 
known compounds of carbon. 



CHAPTER XIV. 

ATOMIC THEORY — ATOMIC WEIGHTS — MOLECULAK 
WEIGHTS — VALENCE — CLASSIFICATION OF THE 
ELEMENTS. 

The Laws of Chemical Action. — You have learned that 
there are two laws always governing chemical combination. 
These are the laws of definite and multiple proportions. 
These laws are simply statements that sum up what has 
been found to be true in all cases examined. They are 
statements of facts discovered by actual experiment. 

We may Know a Fact without Knowing its Cause. — It 
is one thing to know a general fact, and quite another to 
know the cause of the fact. We know that all bodies are 
attracted by the earth, and that they fall when thrown 
into the air. But we do not know why this is so. So, 
too, though we know that substances combine according 
to the laws of definite and multiple proportions, it does 
not necessarily follow that we know why they combine 
according to these laws. 

Hypothesis and Theory. — When a law has been discov- 
ered by careful study of the facts, the next thing to be 
done is to imagine a cause. We try to imagine a condition 
of things which, if it existed, would lead to the results 
discovered. K we succeed in imagining such a condition 

135 



136 THE ELEMENTS OF CHEMISTRY. 

of things we suggest an hypothesis, li, now, we test this 
hypothesis in every way that suggests itself, and find that 
all facts discovered are in accordance with it, we then call 
it a theory. An hypothesis is a guess in regard to the 
cause of certain phenomena. A theory is an hypothesis 
which has been thoroughly tested, and which is applicable 
to a large number of related phenomena.* 

The Atomic Theory. — The atomic theory was suggested 
to account for the laws of definite and multiple propor- 
tions. The theory is this : 

That all hinds of matter are made up of i7idivisible par- 
ticles called atoms; and that the atoms of the different 
elements have different tveights. 

Now if, when substances act upon one another, the 
action takes place between these atoms, and consists either 
in a union or separation of the atoms, then it is easy to 
understand why compounds are formed according to the 
law of definite and multiple proj)ortions. If two elements 
whose atoms have weights which are to each other as 2 to 
9 combine so that one atom of the one combines with one 
atom of the other, then the compound which is formed 
will contain the elements in the proportion of 2 parts by 
weight of the one to 9 parts by weight of the other 
element. If they combine so that one atom of the first 
element combines with two atoms of fche other, then the 

* Hypotheses and theories are of great value to science, if founded 
upon a thorough knowledge of the facts to which they relate. They 
become dangerous when used by those who are not familiar with 
the facts. The student who has not received a thorough scientific 
training should remember that theories and hypotheses, to be of 
value, must be suggested, not by a superficial but by a thorough 
knowledge of the facts. 



ATOMIC THEORY— yALENCE. 137 

resulting compound will contain the elements in the pro- 
portion of 2 parts by weight of the one to 18 parts by 
weight of the other element. 

Atomic Weights. — The weights of the elements which 
have thus far been referred to as comihining lueights are^ in 
accordance with the atomic theory, the relatiye weights of 
the atoms, or the atomic weights. The symbols of the 
elements represent atoms of the elements. Thus, H 
represents an atom of hydrogen, an atom of oxygen, 
etc. As hydrogen enters into combination in smaller 
proportion than any other element, its combining weight 
or atomic weight is taken as the unit. When we say that 
the atomic weight of oxygen is 16, we mean that the atom 
of oxygen is 16 times heavier than that of hydrogen. 

Molecules. — As the symbols of the elements represent 
atoms, so the symbols of compounds represent combina- 
tions of atoms. The symbol of hydrochloric acid, HGl 
represents, according to the theory, the smallest particle 
of this substance that can exist. It is made up of an atom 
of hydrogen and an atom of chlorine, which are combined 
chemically. The symbols HKO3 ? H^O, ISTHg are intended 
to represent the smallest particles of the compounds that 
can exist. The smallest particle of nitric acid consists of 
1 atom of nitrogen, 1 atom of hydrogen, and 3 atoms of 
oxygen. These smallest particles of compounds are called 
molecules. The molecules are made up of atoms. The 
weight of a molecule is equal to the sum of the weights of 
the atoms of which it is composed. 

Avogadro^s Hypothesis. — A careful study of the conduct 
of gases led to the conclusion that equal volumes of all 
gases under the same coiiditions of temperature and pres- 



138 THE ELEMENTS OF CHEMISTRY, 

sure contain the same numler of molecules. This is known 
as Avogadro^s hypothesis. 

The Relative Weights of Molecules Determined by 
Weighing Gases. — If Avogadro^s hypothesis is true, then 
by weighing equal volumes of gaseous substances we can 
learn the relative weights of the molecules of these sub- 
stances. 

Atomic Weights Learned from Molecular Weights. — If 
we knew the molecular weights of all compounds we could 
easily determine the atomic weights of the elements. It 
would only be necessary to select the smallest quantity of 
an element which occurs in any of its compounds. Thus^ 
for example^ if we were to examine all known oxygen 
compounds that can be studied in the form of gas or 
vapor, we should find that the smallest quantity of oxygen 
found in any molecule is represented by 16. 

Valence. — The formulas of the compounds thus far con- 
sidered have all been determined by exactly the same 
methods. On comparing the formulas of the simplest 
hydrogen compounds of chlorine, oxygen, nitrogen, and 
carbon a curious difference is observed. The formulas are 

CIH, OH,, NH3, CH,. 

According to the atomic theory these expressions mean 
that the molecule of hydrochloric acid consists of 1 atom 
of chlorine combined with 1 atom of hydrogen; the mole- 
cule of water consists of 1 atom of oxygen combined with 
2 atoms of hydrogen; the molecule of ammonia of 1 atom 
of nitrogen and 3 atoms of hydrogen; and the molecule 
of marsh-gas of 1 atom of carbon and 4 atoms of hydrogen. 
It appears, therefore, that the atom of oxygen can hold in 



ATOMIC THEORY— FAIENCE, 139 

combination twice as many hydrogen atoms as the atom 
of chlorine can; that the atom of nitrogen can hold three 
times as many; and the atom of carbon four times as 
many. Other atoms differ from one another in the same 
way. 

That property of an element by virtue of which its atom 
can hold in combination a definite number of other atoms 
is called valence. 

Kinds of Elements. — As far as the number of other 
atoms which it can hold in combination is concerned, the 
chlorine atom represents the simplest class of atoms. As 
one chlorine atom can hold but one hydrogen atom in 
combination, so one hydrogen atom can hold but one chlo- 
rine atom. Either the hydrogen atom or the chlorine atom 
maybe taken as an example of the simplest kind of atom. 
An element like hydrogen or chlorine is called a imivalent 
element; an element like oxygen whose atom can hold two 
unit atoms in combination is called a iivalent elemeiit; an 
element like nitrogen whose atom can hold three unit 
atoms in combination is called a trivalent element; and an 
element like carbon whose atom can hold four unit atoms 
in combination is called a quadrivalent element. Most 
elements belong to one or the other of these four classes. 

[Calcium forms with chlorine the compound CaCl^. 
What is the valence of calcium ? Potassium and sodium 
form chlorides of the formulas KCl and NaCl respectively. 
What is the valence of these elements ? Sulphur forms 
with hydrogen a compound of the formula SH^. What 
is the valence of sulphur ?] 

Substituting Power of the Elements. — In the formation 
of salts you have seen that the hydrogen of acids is dis- 



I40 THE ELEMENTS OF CHEMISTRY, 

placed by metals. In such cases one atom of a univalent 
metal takes the place of one atom of hydrogen, one atom 
of a bivalent metal takes the place of two atoms of 
hydrogen, etc. Thus potassium and sodium are univalent. 
In the formation of potassium nitrate from nitric acid, 
IINO3, one atom of potassium displaces one atom of 
hydrogen in the molecule of nitric acid, forming the salt 
KNO3. So also sodium nitrate is NaNOg. In the mole- 
cule of sulphuric acid, H2S0^, there are two atoms of 
hydrogen. To displace these, two atoms of a univalent 
element are required. Thus, potassium sulphate is K2S0^, 
and sodium sulphate is NagSO^. Examples of salts con- 
taining bivalent metals are the following: zinc sulphate, 
ZnSO^, in which one atom of bivalent zinc has displaced 
the two atoms of hydrogen of the sulphuric acid ; barium 
sulphate, BaSO^, in which one atom of bivalent barium 
has displaced the two atoms of hydrogen of sulphuric acid. 
When a bivalent metal forms a salt with an acid like hydro- 
chloric acid, which contains but one atom of hydrogen 
in the molecule, it is believed that one atom of the metal 
acts upon two molecules of the acid, thus : 

Zn+ HCl = z,|Cl_^jj^^ 

or 

Zn + 2HC1 = ZnCl, + H,. 

The formula of zinc nitrate is similar, viz. , Zn(EO^^. 
In the case of trivalent elements the matter is a little more 
complicated, but still simple enough if it be borne in mind 
that a univalent atom takes the place of one atom of 
hydrogen; a bivalent atom takes the place of two atoms 



CLASSIFICATION OF THE ELEMENTS, 141 

of hydrogen; a trivalent atom takes the place of three 
atoms of hydrogen, etc. 

Classification of the Elements. 

Acid Properties and Basic Properties. — The chemical 
properties that force themselves upon our attention most 
prominently in whatever field of chemistry we may be 
working are those which are known as acid properties and 
basic jjroperties. As has already been pointed out, these 
two kinds of properties are the opposite of each other. 
No matter how much chemistry may grow, it is certain 
that the distinction between these two kinds of properties 
will always be recognized as important. 

Acid-forming Elements and Base-forming Elements. — In 
general, both acids and bases contain hydrogen and 
oxygen. There are some elements lohose co7n2JOunds ivith 
hydrogen and oxygen have basic properties, and others 
lohose compounds luith hydrogen and oxygen have acid 
properties. This important fact may be used as the basis 
of a partial classification of the elements. According to 
this, we have (1) acid-forming elements and (2) base-form- 
ing elements. Examples of the first class are chlorine, 
nitrogen, and sulphur. Examples of the second class are 
sodium, calcium, magnesium, etc. The last mentioned 
are generally called metals, and the acid-forming elements 
are generally called non-metals. 

Families of Elements. — Another important fact which is 
soon recognized in studying the elements is that they fall 
into families according to their chemical properties, the 
members of the same family showing striking resemblances 



142 THE ELEMENTS OF CHEMISTRY, 

among one another. Thus, there is the chlorine family, 
which includes, besides chlorine itself, bromine, iodine, 
and fluorine. Further, there is the sulphur family, con- 
sisting of the closely related elements sulphur, selenium, 
and tellurium; besides other families. In all these cases 
the resemblance between members of the same family is 
striking. 

Families of the Acid-forming Elements. — First, we shall 
have the following families to deal with : 

Chlorine Family. Sulphur Family. Nitrogen Family. Carbon Family. 

Chlorine, Sulphur, Nitrogen, Carbon, 

Bromine, Selenium, Phosphorus, Silicon. 

Iodine, Tellurium. Arsenic, 

Fluorine. Antimony. 

As the object of your present study is to get a general 
idea of the principles of chemistry, it will not be necessary 
to go into details in dealing with these families. One 
member of each family, except the sulphur family, having 
been treated comparatively fully, the other members may 
be treated briefly. The members of the sulphur family 
resemble oxygen somewhat, but also differ from it in many 
respects. It will thus be possible to get a clearer idea of 
the principles of chemistry than by attempting to study a 
large number of facts. 



CHAPTEE XV. 

THE CHLORINE FAMILY: CHLORINE, BROMINE, 
IODINE, FLUORINE. 

Introduction. — The three members of this family which 
show the most marked resemblance are chlorine, bromine, 
and iodine. 

Bromine {At. Wt. 80). — This element occurs in nature 
in company with chlorine. Chlorine, as has been stated, 
occurs mostly in combination with sodium, as sodium 
chloride, or common salt. In seyeral of the great salt- 
beds there is some bromine in the form of sodium 
bromide, NaBr, and in some places it occurs as potassium 
bromide, KBr. 

Preparation of Bromine. — The method is the same as 
that made use of for extracting chlorine. In order to get 
chlorine out of common salt, the salt is first converted 
into hydrochloric acid, and this is then oxidized. So, too, 
in order to get bromine out of sodium bromide, the 
bromide must first be converted into hydrobromic acid, 
and this then oxidized. The reactions are 

2NaBr + H^SO, = Na^SO, + 2HBr; 

2HBr + = H,0 + 2Br. 

143 



144 THE ELEMENTS OF CHEMISTRY, 

On the large scale bromine is made by treating mag- 
nesium bromide, MgBr^, with chlorine : 

MgBr^ + 2C1 = MgCl, + 2Br. 

Properties of Bromine. — At ordinary temperatures 
bromine is a heavy dark-red liquid which is easily con- 
verted into a brownish-red vapor. It has an extremely 
disagreeable odor. Hence its name from a Greek word 
meaning a stench. Its properties are, in general, like 
those of chlorine. It acts violently uj)on organic sub- 
stances. It attacks the skin and the membranes lining, 
the passages of the throat and lungs. Wounds caused by 
the liquid coming in contact with the skin are painful and 
heal with difficulty. It must, therefore, be handled with 
great care. It combines with many element* directly and 
with great energy, its compounds with other elements 
being called Iromides. While acting in general in the 
same way as chlorine, it is a somewhat weaker element, so 
that chlorine drives it out of its compounds and sets it 
free. 

Experiment 83. — Mix together about 1 gram of potassium 
bromide and 2 grams of manganese dioxide. Pour .upon the 
mixture, in a good-sized test-tube, sufficient dilute sulphuric acid 
to cover it. Heat gently. What do you observe ? Perform this 
experiment where there is a good draught. 

Hydrobromic Acid, HBr. — The only compound which 
bromine" forms with hydrogen alone is hydrobromic acid. 
This is in all respects very much like hydrochloric acid. 

Experiment 84.— In a test-tube put a few crystals of potassium 
bromide. Pour on them a few drops of concentrated sulphuric 
acid. White fumes of hydrobromic acid and reddish-brown 
vapor of bromine are noticed. Treat a few crystals of potassium 
or sodium chloride in the same way. What difference is there 



THE CHLORINE FAMILY, 145 

between the two cases? The explanation of the. difference ob- 
served is that sulphuric acid decomposes hydrobromic acid, set- 
ting bromine free, while it does not decompose hydrochloric acid. 

Compounds with Hydrogen and Oxygen. — With hy- 
drogen and oxygen bromine forms componnds which 
resemble yery closely those which chlorine forms with the 
same elements. The principal ones are hromic, HBrOg, 
and. hifpolromotts acids, HBrO^ which are like chloric and 
hypochlorous acids. 

Iodine, I {At. Wt. 127). — This element occurs in nature 
in combination with sodium, in company with chlorine 
and bromine, but in smaller quantity than either. It is 
also found in larger quantity in sea-plants. It is obtained 
largely from the latter source. On the coasts of Scotland 
and France the sea-weed which is thrown up by storms is 
gathered, dried, and burned. The organic portions are 
thus destroyed [what is the meaning of the word destroyed 
used in this sense ?], and the mineral or earthy portions 
are left behind as ashes. The incombustible residue is 
called kelp. It contains sodium iodide. At present, in 
some parts of the ocean, sea-weed is cultivated for the 
sake of the iodine which it yields. Chili saltpetre, or the 
natural sodium nitrate found in Chili, contains some iodine 
in combination partly as sodium iodide and partly as 
sodium iodate, and this furnishes a considerable quantity 
of the iodine of commerce. 

Preparation of Iodine. — Iodine is prepared from sodium 
iodide, just as chlorine and bromine are prepared from 
their compounds with sodium and potassium. 

Properties of Iodine. — At ordinary temperatures iodine 
is a grayish-black, crystallized solid. It melts easily and 
boils, forming a violet-colored vapor. 



146 THE ELEMENTS OF CHEMISTRY. 

Experiment 85. — Mix about 1 gram potassium iodide with 
about twice its weight of manganese dioxide. Treat with a little 
sulphuric acid in a test-tube. Heat gently. Gradually the tube 
will be filled with the beautiful colored vapor of iodine. In the 
upper part of the tube some of the iodine will be deposited in the 
form of crystals of a grayish-black color. 

Iodine dissolves slightly in water, easily in alcohol and 
in a water solution of potassium iodide. 

Experiment 86. — Make solutions of iodine in water, in alcohol, 
and in a water solution of potassium iodide. Use small quanti- 
ties in test-tubes. 

When a solution containing /ree iodine is treated with a 
little starch-paste the solution turns blue, in consequence 
of the formation of a complicated compound of starch and 
iodine. Bromine and chlorine do not form blue com- 
pounds. Advantage is taken of this fact to distinguish 
between iodine and other members of the family. 

Experiment 87. — Make some starch-paste by covering a few 
grains of starch in a porcelain evaporating-dish with cold water, 
grinding this to a paste, and pouring 200-300 c.c. boiling hot 
water on it. After cooling add a little of this paste to a dilute 
solution of iodine in potassium iodide. What change takes 
place ? Now add a little of the paste to a diluted water solution 
of potassium iodide. Is there any change of color ? Add a drop 
or two of a solution of chlorine in water. What takes place ? 
Explain what you have seen. Does chlorine alone form a blue 
compound with starch ? 

Hydriodic Acid, HI, is analogous to hydrochloric and 
hydrobromic acids. It is set free from the iodides by 
treating them with sulphuric acid; but it is even more 
-instable than hydrobromic acid, and hence breaks down 
into hydrogen and iodine. The iodine is set free, while 
the hydrogen acts on the sulphuric acid, as it does in the 
case of hydrobromic acid. 



THE CHLORINE FAMILY, 147 

Experiment 88. — Treat a few small crystals of potassium iodide 
with sulphuric acid. [What do you notice ?] Compare with the 
results obtained when potassium bromide and sodium chloride 
are used. 

Fluorine occurs in nature in large quantity, and widely 
distributed, but always in combination with other elements. 
It is found chiefly in combination with calcium, as fliior 
spar, or calcium fluoride, G'ixF^, and in combination with 
sodium and aluminium, as cryolite, a mineral which 
occurs abundantly in Greenland, and has the composition 
SlSTaF . AIF3, or NagAlF^, being a complex compound of 
sodium fluoride and aluminium fluoride. It is prepared 
by passing an electric current through liquid hydrofluoric 
acid containing potassium fluoride in solution in a vessel 
of platinum or copper. 

It is the most active of all the elements at ordinary 
temperatures. It is a greenish-yellow gas. 

Hydrofluoric Acid, HF, is made from fluor spar by 
treating it with sulphuric acid. The action is of the same 
kind as that which takes place when hydrochloric acid is 
liberated from sodium chloride: 

CaF, + H^SO, = CaSO, + 2HF. 

Hydrofluoric acid is a colorless gas, with strong acid 
properties. It greatly irritates the membranes lining the 
throat and lungs, and hence care should be taken not to 
inhale it. It acts upon glass, decomposing it, and must 
therefore be kept in vessels of rubber, lead, or platinum, 
upon which it does not act. 

Etching on Glass. — The acid is used for etching on 
glass, particularly for marking scales on thermometers, 
barometers, and other graduated glass instruments. A 



143 THE ELEMENTS OF CHEMISTRY. 

solution of the gas in water is manufactured for this pur- 
pose and kept in rubber bottles. 

Experiment 89. — A lead or platinum vessel put a few grams 
(5-6) of powdered fluor spar, and pour on it enough concentrated 
sulphuric acid to make a thick paste. Cover the surface of a 
piece of glass with a thin layer of wax or paraffin, and through 
this scratch some letters or figures, so as to leave the glass ex- 
posed where the scratches are made. Put the glass with the 
waxed side downward over the vessel containing the fluor spar, 
and let it stand for some hours. Then take off the glass, scrape 
oft' the coating, and the figures which were marked through the 
wax or paraffin will be found etched on the glass. 

Comparison of the Members of the Chlorine Family. — In 

considering, first, the physical properties of these ele- 
ments, you notice that all form colored gases or vapors. 
At ordinary temperatures fluorine and chlorine are gases, 
bromine is a liquid, and iodine a solid. In regard to their 
chemical conduct, it may be said that, in general, fluorine 
is the most active; chlorine comes next in order, then 
bromine, and lastly iodine. 

Their Compounds. — The compounds formed by the three 
elements chlorine, bromine, and iodine with hydrogen and 
oxygen have analogous compositions, and are formed by 
analogous reactions. Thus, there are the hydrogen com- 
pounds : 

HCl, HBr, and HI; 

and the compounds with hydrogen and oxygen : 

HCIO, HBrO. — 

HCIO,. — — 

HCIO3, HBr03, HIO3. 

HCIO,, HIO,. 



THE CHLORINE FAMILY, 149 

Relations between the Atomic Weights. — On comparing 
the atomic weights of chlorine, bromine, and iodine, it 
will be seen that the atomic weight of bromine, which is 
80, is^ nearly the mean of the atomic weights of chlorine 
and iodine. 

35.5 + 127 = 162.5; 

At. Wt. of At. Wt. of 

chlorine. iodine. 

162.5 
and ' = 81.25, which is nearly the atomic weight of 

bromine. 

Relation between the Properties of the Elements and 
their Atomic Weights. — The inoperties of the three elements 
— chloriney Iromiiie^ and iodine — vary tuith the variations 
in their atomic weights^ or with the loeights of their atoms. 
The gradation in properties takes place in the order 
fluorine, chlorine, bromine, iodine, and this is also the 
order in which the atomic weights increase. This may be 
a mere coincidence, but we shall find that in the other 
families there are similar indications of a close connection 
between the weights of the atoms of the elements iand their 
physical and chemical properties. 



CHAPTER XVI. 

THE SULPHUR FAMILY: SULPHUR, SELENIUM, 
TELLURIUM. 

Sulphur, S {At. Wt. 32). — The principal member of this 
family is sulphur. In nature it is often accompanied by 
small quantities of selenium, and sometimes by tellurium. 
It has been known in the elementary form from the 
earliest times, for the reason that it occurs abundantly in 
this form in nature. It is found particularly in the 
neighborhood of volcanoes, as in Sicily, which is the chief 
source of the sulphur of commerce. It occurs, further, in 
combination with many metals as sulphides, — as in iron 
pyrites, FeS2; copper pyrites, FeCuS2; galenite, PbS, etc.; 
in combination with metals and oxygen as sulphates, — for 
example, as calcium sulphate, or gypsum, CaSO^ + ^H^O; 
barium sulphate, or heavy spar, BaSO^; lead sulphate, 
PbSO^; and in a few vegetable and animal products in 
combination with carbon, hydrogen, and, generally, with 
nitrogen. 

Extraction of Sulphur from its Ores. — When taken from 
the mines, sulphur is mixed with many earthy substances 
from which it must be separated. This separation is 
accomplished by piling the ore in ^uch a way as to leave 

150 



THE SULPHUR FAMILY, 151 

passages for air. The 2)iles are covered with some material 
to prevent free access of air, and the mass is then lighted 
below. A part of the sulphur burns, and tlie heat thus 
furnished melts the rest of the sulphur. The molten 
sulphur runs down to the bottom of the pile, and is drawn 
oflE from time to time. 

[If the pile were not protected from free access of air 
what would become of the sulphur ? What analogy is 
there between this process and that made use of in making 
charcoal ? What are the essential diiferences between the 
two processes ?] 

How Sulphur is Refined. — The crude brimstone first 
obtained is afterwards refined by distillation, and it is this 
distilled sulphur that is met with in commerce under the 
names ^^roU brimstone, ^^ '^^ stick sulphur,'^ and ^^ flowers 
of sulphur.'^ The distillation is carried on in earthenware 
retorts connected with large chambers of brick- work. 
When the vapor of sulphur first comes over into the con- 
densing chamber it is suddenly cooled, and hence deposited 
in the form of fine powder. This is what is called 
'' flowers of sulphur. ^^ After the distillation has continued 
for some time the vapor condenses in the form of a liquid, 
which collects at the bottom of the chamber. This is 
drawn off into wooden moulds and takes the form of '' roll 
brimstone^' or '^^ stick sulphur. ^^ 

Properties of Sulphur. — Sulphur is a yellow, brittle sub- 
stance which at — 50° is almost coioriess. It melts at 
ll-i^'.S, forming a thin, straw-colored liquid. When 
heated to a higher temperature it becomes darker and 
darker in color, and at 200° to 250° it is so thick that the 
vessel containing it may be turned upside down without 



152 THE ELEMENTS OF CHEMISTRY, 

danger of runuing out. Finally, at 448°. 4 it boils and is 
then converted into a brownish-j^ellow vapor. 

Experiment 90. — Distil about 10 grams of roll sulphur from 
ah ordinary glass retort. The retort should not be connected with 
a condenser. Notice the changes above described. Collect the 
liquid sulphur which passes over in a beaker-glass containing cold 
water. 

The sulphur collected in this experiment is at first quite elastic. 
On standing it becomes brittle. 

Crystals of Sulphur. — When molten sulphur solidifies, 

or when it is deposited from a solution, its particles 

arrange themselves in regular forms called crystals. But, 

strange to say, the crystals formed from molten sulphur 

are entirely different from those deposited from solutions 

of sulphur. Substances which crystallize in two distinct 

forms are called climorijhous. Carbon, like sulphur, 

crystallizes in two different forms [what are they ?], and 

is hence dimorphous. 

Experiment 91. — In a covered sand or Hessian crucible melt 
about 20 grams of roll sulphur. Let it cool slowly, and when a 
thin crust has formed on the surface make a hole through this 
and pour out the liquid part of the sulphur. The inside of the 
crucible will be found lined with honey-yellow needles. Take 
out a few crystals and examine them. — Are they brittle or elas- 
tic ? What is their color? Are they opaque, transparent, or 
translucent ? — Lay the crucible aside, and in the course of a few 
days again examine the crystals.— What changes, if any, have 
taken place ? 

Solution of Sulphur. — Sulphur is insoluble in water, 

slightly soluble in alcohol and ether. It dissolves in the 

liquid compound of carbon and sulphur known as carbon 

bisulphide, CS2, and from this solution it is deposited in 

crystals quite different from those obtained in Experiment 

91, 



THE SULPHUR FAMILY, 153 

Experiment 92. — Dissolve 2 to 3 grams roll sulphur in 5 to 10 
c.c. carbon disulphide. Put the solution in a small beaker, and 
allow the carbon bisulphide to evaporate by standing in the air. 
What is the appearance of the crystals ? Are they dark yellow 
or bright yellow ? Are they brittle or elastic ? [State in tabular 
form the properties of the two allotropic forms of sulphur.] 

Chemical Conduct of Sulphur. — Sulphur combines with 

oxygen w^hen heated to a sufficiently high temperature. 

The product is sulphur dioxide, SO2. [Is there any 

analogy between carbon and sulphur in this respect ?] It 

combines readily with most metals, forming sulphides. 

Its combination with iron has already been shown in 

Experiment 12. It also combines with copper, the act 

being accompanied by light and heat. 

Experiment 93. — In a wide test-tube heat some sulphur to 
boiling. Introduce into it small pieces of copper-foil or sheet 
copper. Or hold a narrow piece of sheet copper so that the end 
just dips into the boiling sulphur. What evidence have you that 
action takes place ? 

Hydrogen Sulphide, Sulphuretted Hydrogen, H^S. — 

When hydrogen is passed oyer highly heated sulphur the 

two elements combine to form hydrogen sulphide. [Is 

there any analogy between this process and the formation 

of water by the burning of hydrogen ?] This compound 

of sulphur and hydrogen occurs in nature in solution in 

the so-called ^'sulphur waters, ^^ which are met with in 

many parts of this and other countries. It also issues from 

the earth in some places. It is formed by heating organic 

substances that contain sulphur, just as water is formed 

by heating organic substances that contain oxygen, and 

ammonia by heating such as contain nitrogen. It is 

formed, further, by decomposition of organic substances 

which contain sulphur, as, for example, the albumen of 



1S4 THE ELEMENTS OF CHEMISTRY. 

eggs. The odor of rotten eggs is partly due to the forma- 
tion of hydrogen sulphide. [How is it . that paraffin, 
p. 117, heated with sulphur gives off hydrogen sulphide?] 
Preparation of Hydrogen Sulphide. — It is made in the 
laboratory by treating a sulphide with an acid. When 
sulphuric acid acts upon iron sulphide, hydrogen sulphide 
is given off thus: 

FeS + H^SO, = FeSO, + H,S. 

Hydrochloric acid acts in a similar way: 

FeS + 2HC1 = FeCl, + H,S. 

Experiment 94. — Arrange an apparatus as shown in Fig. 14. 
Put r^ small handful of sulphide of iron, FeS, in the flask, and 
pour dilute sulphuric acid upon it. Pass the gas through a little 
water contained in the wash-cylinder A. Pass some of the gas 
into water. What evidence have you that it dissolves ? — Collect 
some by displacement of air. It is heavier than air (specific grav- 
ity 1.178). Should the vessel be placed with the mouth down or 
up ? Set fire to some of the gas contained in a cylinder. If there 
is free access of air the sulphur burns to sulphur dioxide, and the 
hydrogen to water. 

Properties of Hydrogen Sulphide. — Hydrogen sulphide, 
or, as it is commonly called, sulphuretted hydrogen, is a 
colorless, transparent gas. It has a disagreeable odor, 
somewhat resembling that of rotten eggs. It is poisonous 
when inhaled in any quantity. It dissolves in water, 
forming a solution which has the odor of the gas. Most 
metals when heated in the gas are converted into sulphides. 
Thus, when it is passed over heated iron this reaction 
takes place: 

Fe + H,S = FeS + H,. 

[What takes place when water vapor is 23assed over 
heated iron ?1 



THE SULPHUR FAMILY, 155 

Precipitation of Sulphides. — Many of the sulphides are 
insoluble in water. Hence, when hydrogen sulphide is 
passed througli solutions containing metals in the form of 
soluble salts^ the insoluble sulphides are thrown down, or 
jorecipitated. 

Experiment 95. — Pass hydrogen sulphide successively through 
solutions containing a little lead nitrate^ zinc sulphate^ and 
arsenic chloride prepared by dissolving a little white arsenic, or 
arsenic trioxide^ AS2O3, in dilute hydrochloric acid. What do 
you observe in each case ? — The substances formed are respectively 
the sulphides of lead, zinc, and arsenic. The reaction in the case 
of zinc sulphate is represented thus : 

ZnS04 + H3S = ZnS + H2SO4. 

Chemical Analysis.— In dealing with chemical sub- 
stances the first thing we have to determine is their com- 
position, or, in other words, we have to analyze them. 
For this purpose we must first know the properties of the 
elements and their conduct towards chemical substances. 
To facilitate the process of analysis the mixture to be 
examined is usually brought into solution and then treated 
successively with certain substances, the effect being 
observed in each case. Suppose we had a solution con- 
taining most of the metallic elements in the form of salts. 
If we were to pass hydrogen sulphide through this solu- 
tion, some of the metals would be precipitated as sul- 
phides, while others would remain in solution, as their 
sulphides are soluble. The precipitated sulphides could 
then be filtered off and examined, and the filtered solution 
also could be further examined. Hydrogen sulphide is 
constantly made use of in the laboratory for the purposes 
of analysis. 



156 



THE ELEMENTS OE CHEMISTRY, 



Compounds of Sulphur with Oxygen, and with 
Hydrogen and Oxygen. 

Formation of the Compounds of Sulphur. — When sulphur 
burns in the air, the dioxide, SO2, is formed. Under 
certain conditions the dioxide combines with more oxygen, 
forming the trioxide, SO3. When sulphur dioxide acts 
upon water, sid2Jhtcroiis acid is formed : 

so, + H,0 = H,SO,. 

[What analogy is there between the acid thus formed 

and carbonic acid ?] 

When the trioxide combines with water, sidjjJiuric acid 

is formed : 

SO3 + H,0 = H^SO,. 

Sulphur Dioxide, SO2. — This compound is formed by 

burning sulphur in the air or in oxygen. It issues from 

volcanoes in large quantities. It can be prepared by 

heating copper with sulphuric acid and by 

treating a sulphite with sulphuric acid. 

Experiment 96. — Arrange an apparatus as 
shown in Fig. 36. J. is a funnel-tube provided 
with a stop-cock. In the flask put a 40 per cent 
solution of acid sodium sulphite, HNaSOa ; in the 
funnel, after closing the stop-cock, put ordinary 
concentrated sulphuric acid. Open the stop-cock 
very little so that the sulphuric acid drops into the 
solution below. A regular evolution of sulphur 
dioxide can thus be maintained. Pass some of the 
gas into a bottle containing water. Fill a vessel 
Fig. 36. ^y displacement of air. It is more than twice 

as heavy as air. See whether the gas will burn or support com- 
bustion. 

SHNaSOa + HaS04 = Na^SO* + 2SO2 + SH^O. 




THE SULPHUR FAMILY, 157 

Properties of Sulphur Dioxide.---Sulphiir dioxide is a 
colorless gas of an unpleasant, suffocating odor, familiar 
to every one as that of burning sulphur-matches. Water 
dissolves it readily. It bleaches readily, and stops fermen- 
tation. 

Experiment 97. — Burn a Uttle sulphur in a porcelain crucible 
under a bell-jar. Place over the crucible on a tripod some 
flowers. In the atmosphere of sulphur dioxide the flowers will 
be bleached. 

Uses of Sulphur Dioxide. — It is used extensively for the 
purpose of bleaching wool, silk, straw, paper, etc. ; and, 
further, to preserve liquids that have a tendency to 
undergo fermentation. If left in the air, fruit-juices be- 
come sour in consequence of fermentation. As sulphur 
dioxide prevents fermentation, the juices are kept sweet if 
treated with something which gives off the gas, as, for 
example, a sulphite. The principal use of sulphur dioxide 
is in the manufacture of sulphuric acid. For this purpose 
it is made in enormous quantities. 

Sulphurous Acid and Sulphites. — The solution of sulphur 
dioxide in water has acid properties, and contains the acid 
HjjSOg. By neutralizing the solution with bases, the 
sulphites, or salts of sulphurous acid, are obtained. The 
sulphites are analogous to the carbonates in composition, 
and suffer the same decomposition when treated with 
acids. When a carbonate is treated with an acid, carbon 
dioxide is given off. So, also, when a sulphite is treated 
with an acid, sulphur dioxide is given off : 

]Sra,S03 + H^SO, =: Na^SO, -f H,0 + SO,; 
Na,S03 + 2HC1 ^ 2NaCl + 11,0 + SO,. 



15^ THE ELEMENTS OF CHEMISTRY. 

Sulphuric Acid, H^SO^. — Salts of sulphuric acid are 
found in nature, as gypsum, heavy spar, etc. It cannot 
easily be prepared from its salts, as hydrochloric and nitric 
acids are prepared, and is made exclusively by oxidizing 
sulphur dioxide. The reactions involved in the manufac- 
ture of sulphuric acid are : 

S + 0, .:. SO,; 

SO, +H,0-H,S03; 
H,S03 +0 = H^SO,. 

Or sulphur dioxide is oxidized to the trioxide, and this 
then treated with water, in which case the reactions are : 

S0, + =:S03; 
SO3 + H,0 = H,SO,. 

How Nitric Oxide Acts in Oxidizing Sulphurous Acid. — 

The older method of making sulphuric acid depends partly 
upon the power of nitric oxide, NO, to combine directly 
with the oxygen of the air to form nitrogen peroxide, 
NO,. Nitrogen peroxide gives up half its oxygen to sul- 
phurous acid, and is itself thus reduced to nitric oxide. 
If, therefore, sulphur dioxide, water, and nitrogen peroxide 
are brought together, the first action is represented thus: 

SO, + H,0 + NO, = H,SO, + NO. 

Now, if air is supplied, the nitric oxide is converted into 
the peroxide: 

NO + = N0,. 

The peroxide acting upon a further quantity of sulphur 
dioxide and water is again reduced, and so on indefinitely. 
It will thus be seen that, starting with a small quantity 



THE SULPHUR FAMILY, 



159 



of nitric oxide, it should be possible to convert a large 
quantity of sulphur dioxide into sulphuric acid. 

Manufacture of Sulphuric Acid. — In the manufacture of 
sulphuric acid by the older and ordinary method sulphur 
or iron pyrites, FeS2 , is burned. In the former case, the 
only product of the combustion is sulphur dioxide; in the 
latter case, the sulphur forms sulphur dioxide, and the 
iron is converted into an oxide, Fe203. The sulphur dioxide 
thus formed is conducted into large chambers lined with 
lead, for the reason that sulphuric acid does not act upon 
lead, while it does act upon most other common metals. 
Instead of starting with nitric oxide, nitric acid is passed 
into the chambers, and water in the form of steam. The 
first action between the nitric acid, steam, and sulphur 
dioxide is this : 

2HNO3 + 3SO2 + 2H2O = SH^SO, + 2N0. 

From this point sulphur dioxide, water, and nitric oxide 
are brought into action, and the chief reactions are those 
described above. 

A Leaden Chamber. — The arrangement of a leaden 
chamber is shown in Fig. 37. The furnace in which the 




Fig. 37. 



sulphur or iron pyrites is burned is represented by /. 
Steam from the boiler I is forced into the chamber 



i6o THE ELEMENTS OF CHEMISTRY. 

through jets. The nitric acid is formed from sodium 
nitrate and sulphuric acid in the furnace n, A good 
draught is kept up by means of a high chimney. 

New Method for the Manufacture of Sulphuric Acid. — A 
simpler method than that above described has recently 
been devised. This consists in making suljjliur trioxide 
by causing sulphur dioxide and oxygen to unite, tinder 
ordinary circumstances sulphur dioxide does not combine 
with more oxygen. When it is passed with air or oxygen 
over various substances such as platinum and an oxide of 
iron in a finely divided state, it unites with oxygen to form 
the trioxide. When the trioxide is brought together with 
water sulphuric acid is formed. 

Ordinary Sulphuric Acid: Oil of Vitriol. — The acid 
obtained from the chambers is evaporated in lead pans, 
and afterwards in platinum or glass or cast-iron pans. The 
strong acid thus obtained is the concentrated sulphuric acid 
of commerce, which is commonly called oil of vitriol. It 
is an oily liquid, usually somewhat colored by impurities. 

The pure acid is a colorless liquid at ordinary tempera- 
tures. When cooled down it forms crystals. It decom- 
poses the salts of most other acids, setting the acids free 
and forming sulphates. You have already had illustrations 
of this power in the liberation of nitric and hydrochloric 
acids from their salts by treatment with sulphuric acid. 

[Give the equations representing the action which takes 
place when common salt and potassium nitrate are treated 
with sulphuric acid.] 

Sulphuric Acid Combines with Water. — Sulphuric acid 
has a very strong tendency to absorb water and form com- 
pounds with it. A great deal of heat is formed in this 



THE SULPHUR FAMILY. i6i 

action. This fact lias been repeatedly illustrated in 
experiments already performed; and attention has been 
called to the necessity for caution in mixing the liquids. 
The acid acts upon organic substances containing hydrogen 
and oxygen, and extracts them in the proportions to form 
water. A piece of wood is charred, if put in the acid, in 
consequence of the abstraction of hydrogen and oxygen. 
[How is carbon monoxide prepared ? How is wood charred 
in the preparation of charcoal ? Is there any analogy 
between the preparation of charcoal in the ordinary way 
and by the action of sulphuric acid ?] 

Wounds caused by sulphuric acid are painful and heal 
with difficulty. 

Importance of Sulphuric Acid. — Sulphuric acid is the 
most important manufactured chemical substance. Most 
chemical industries depend upon it. Among the many 
uses to which it is put are the making of ^^soda^^ or 
sodium carbonate, which is necessary for the manufacture 
of soap and glass ; the making of phosphorus, of artificial 
fertilizers, of glucose, of nitroglycerin, the refining of 
petroleum, etc., etc. 

Monobasic and Dibasic Acids. — Sulphuric acid differs 
markedly from nitric and hydrochloric acids in one 
respect. It has the power to form two different salts with 
the same metal, in one of which there is relatively twice 
as much of the metallic element as in the other. If to a 
given quantity of sulphuric acid there is aded only half the 
quantity of caustic potash required to neutralize it, a salt 
is formed which crystallizes. It has the composition 
represented by the formula KHSO^. If nitric acid is 
treated in the same way, only half the acid is acted on. 



i62 THE ELEMENTS OF CHEMISTRY. 

and this forms ordinary potassium nitrate, KNO3 , the rest 
of the acid being left unacted upon. In the case of sul- 
phuric acid two reactions are possible, viz. : 

H^SO, + KOH = KHSO, + H^O; 
H^S0, + 2K0H= K,S0, + 2H,0. 

In the case of nitric acid only one reaction is possible 
under ordinary circumstances: 

HNO3 + KOH = KNO3 + H,0. 

Acids which, like sulphuric acid, have the power to 
form two salts with the same metal are called dihasic 
acids. Acids which, like nitric acid, have the power 
usually to form only one salt with the same metal are 
called monobasic acids. This power is connected with the 
number of replaceable hydrogen atoms contained in the 
molecule of the acid. An acid containing two replaceable 
hydrogen atoms in its molecule is dibasic; one containing 
only one replaceable hydrogen atom in its molecule is 
monobasic. 

Acid, Neutral, and Normal Salts. — A dibasic acid yields 
two classes of salts: (1) those in which all the hydrogen is 
replaced, and (2) those in which half the hydrogen i§ 
replaced by metal. The former are called normal salts, 
the latter acid salts, Normal salts are generally neutral, 
and are sometimes called neutral salts. 

Carbon Bisulphide, CS2. — Sulphur forms with carbon a 
compound called carbon bisulphide, which has the com- 
position CS2. It is made by bringing carbon and sulphur 
together at high temperatures. It is a liquid that boils 
at 47"". Th^t it dissolves sulphur has been shown in 



THE SULPHUR FAMILY. 163 

Experiments 11 and 92. It also dissolves many other 
substances, as, for example, rubber. 

Selenium, Tellurium, and their Compounds. — These ele- 
ments are comparatively rarely met with. In general 
their properties are similar to those of sulphur, and they 
form compounds analogous to the principal compounds of 
sulphur. 

Relations between the Atomic Weights of Sulphur, Sele- 
nium, and Tellurium. — The relation between the atomic 
weights of the members of the sulphur family is like that 
already noticed between the atomic weights of the members 
of the chlorine family. It is shown thus : 

32 + 127 = 159; 

At. Wt. of At. Wt. of 
sulphur. tellurium. 

159 

and -^ — 79.5, which is nearly 79, the atomic weight of 

selenium. 



CHAPTER XVII. 

THE NITROGEIsr FAMILY: NITROGEN, PHOSPHORUS, 
ARSENIC, AND ANTIMONY. 

BORON AND SILICON. 

Phosphorus, P {At. Wt. 31). — Phosphorus occurs in the 
form of phosphates, or salts of phosphoric acid. The 
chief of these is calcium phosphate, which is the principal 
c'onstituent of the minerals phosphorite and apatite, and of 
the ashes of bones. 

Phosphorus Made from Bones. — It is made from bone- 
ash, which contains a large proportion of calcium phos- 
phate. The ash is first mixed with sulphuric acid. Then 
the compound thus obtained is mixed with charcoal and 
heated, when phosphorus distils over. It is cast into 
sticks under water, and kept under water. 

Properties. — It is colorless or slightly yellow and 
translucent. At ordinary temperatures it can be cut like 
wax, but it becomes hard and brittle at lower tempera- 
tures. It melts at 44°, and boils at 290°. Unless care- 
fully protected from the light its appearance changes. It 
becomes opaque and dark in color, and finally dark red. 
This change can be hastened by heating the phosphorus 
in a sealed tube to 250°. Ordinary phosphorus is insolu- 
ble in water, but soluble in carbon bisulphide. In contact 

164 



THE NITROGEN FAMILY. 165 

with the air it gives off fumes which emit a pale light 

visible in a dark room. It takes fire when rubbed or cut, 

and must hence be handled with great care. It should 

always be cut under water, and never held in the hand. 

It not only combines with oxygen easily, but with other 

elements, such as chlorine, bromine, and iodine. 

Experiment 98. — Bring together in a porcelain crucible or 
evaporating-dish a little phosphorus and iodine. It will be seen 
that simple contact is sufficient to cause the two substances to 
act upon each other. Direct combination takes place, and the 
action is accompanied by light and heat. 

Phosphorus is very poisonous. Its vapor produces a 
disease of the bones. 

Red Phosphorus. — The red substance formed when 
ordinary phosphorus is left in the light, or heated without 
access of air, is a second variety of phosphorus, known as 
red phosphorus. This differs from ordinary phosphorus 
as much as graphite differs from the diamond. Ordinary 
phosphorus is very active, combining readily with oxygen; 
it is soluble in carbon bisulphide; and is poisonous. Eed 
phosphorus, on the other hand, is inactive. It does not 
change in the air, and requires to be heated to a compara- 
tively high temperature before it will combine with 
oxygen; it is insoluble in carbon bisulphide, and is not 
poisonous. It is converted into the ordinary variety when 
heated to about 300°. [Make out a tabular comparison of 
the properties of the two allotropic forms of phosphorus.] 

Uses of Phosphorus. — The principal use of phosphorus 
is in the manufacture of matches. Ordinary friction- 
matches are tipped with a mixture of phosphorus, glue, 
and potassium chlorate. ^^ Safety-matches^^ are usually 
tipped with potassium chlorate and antimony sulphide. 



i66 THE ELEMENTS OF CHEMISTRY, 

The surface upon which they are rubbed is made of red 
phosphorus, black oxide of manganese, and gkie. Mixed 
with flour, phosphorus is frequently used as a rat-poison. 
Compounds of Phosphorus with Oxygen and with Hy- 
drogen and Oxygen. — When phosphorus is burned in the 
air or in oxygen it is converted into the oxide, PgO^. This 
combines with water in different proportions, forming two 
distinct acids, known as nietaphosiJhoric and orthophos- 
phoric acids : 

PA+ H,0 = 2HP03; 

Metaphosphoric acid. 

P,0, + 3H,0 = 3H3PO,. 

Orthopliusphoric acid. 

Orthophosphoric or Ordinary Phosphoric Acid, H3P0^, is 

the principal compound of phosphorus. It is the final 
product of the action of air and moisture on phosphorus. 
As has been stated, it occurs in nature as the calcium salt 
in phosphorite and apatite. This salt is also the chief 
constituent of bone-ash. It is a solid crystallized sub- 
stance, and is made by treating bone-ash with sulphuric 
acid, or by oxidizing phosphorus. It has the power of 
forming three distinct salts with the same metal, and is 
hence called triiasic. With sodium, for example, it forms 
the three salts NagPO,, Na^HPO,, and NaH^PO,. Its 
normal calcium salt — that is to say, the one in which all 
the three acid hydrogen atoms are replaced by calcium- — 
has the formula Ca3(POj2? three bivalent calcium atoms 
replacing six atoms of hydrogen. 

Arsenic and its Compounds. — Arsenic, As {At, Wt. 75), 
occurs in nature in combination with metals, — as, for 
example, iron, copper, cobalt, nickel, etc., — and in com- 
bination with oxygen as the oxide ASgOg, It has a metallic 



THE NITROGEN FAMILY. 



167 



lustre. When heated to quite a high temperature in the 
air it takes fire, and burns with a bluish flame, gi^iiig off 
a smoke which has the odor of garlic and is poisonous. 
It combines directly with most elements. In the elemen- 
tary form it is only slightly poisonous, but when oxidized 
it becomes very poisonous. 

Arsine, Arseniuretted Hydrogen, AsHg. — This com- 
pound, which in composition is analogous to ammonia, 
NH3 , is made by bringing a compound of arsenic into a 
mixture from which hydrogen is being evolved. 

Experiment 99.— Arrange an apparatus as shown in Fig. 38. 
The first horizontal tube contains coarsely granulated calcium 
chloride. Put some granulated zinc iu the flask and pour dilute 




Fig. 38. 

sulphuric acid on it. When the air is all out of the vessel and 
the hydrogen is lighted, add slowly a little of a solution of arsenic 
oxide, AS2O3, in dilute hydrochloric acid. What change takes 
place in the flarae? Is the color changed ? Are fumes given off ? 
(See Experiment 100.) 

Arsine is a colorless gas. It is very poisonous and has 
an unpleasant odor. When lighted it burns with a bluish- 



i68 THE ELEMENTS OF CHEMISTRY. 

white flame. It is very unstable, breaking up into arsenic 
and hydrogen when heated. When a cold object, as a 
piece of porcelain, is brought into the flame of burning 
arsine, the arsenic is deposited in the form of a dark spot. 
Detection of Arsenic in Cases of Poisoning. — The conduct 
of arsine is taken advantage of for the purpose of detect- 
ing the presence of arsenic. It is extensively used in 
examining the stomach and other viscera of human beings 
in cases of suspected poisoning. The method used is 
known as Marsha's test. 

Experiment 100. — Into the flame of the burning hydrogen and 
arsine produced in the last experiment introduce a piece of por- 
celain, as the bottom of a small porcelain dish or a crucible, or a 
bit of a broken plate, and notice the appearance of the spots. Heat 
by means of a Bunsen burner the tube through which the gas is 
passing, which should be of hard glass. Just in front of the 
heated place there will be deposited a thin layer of metallic 
arsenic, commonly called a mirror of arsenic. This deposit is due 
to the decomposition of the arsine into arsenic and hydrogen by 
heat. 

Arsenic Trioxide, AS2O3. — When arsenic is burned in the 
air or oxygen it forms the trioxide. [Compare with 
phosphorus in this respect.] This substance, which is 
what is commonly called arsenic, or white arsenic, is made 
by heating certain natural compounds of arsenic and 
metals in contact with the air. Under these circum- 
stances both the metal and the arsenic are oxidized, -and 
the oxide of arsenic, being volatile, passes off and is 
condensed and collected in large chambers of mason-work. 
It is a colorless, glassy mass, It is difficultly soluble in 
water, more easily in hydrochloric acid. It has a weak, 
disagreeably sweet taste, and acts very poisonously. It is 



THE NITROGEN FAMILY. 169 

probably more frequently used as a poison than any other 
substance. Minufce quantities can be detected by the 
chemist with absolute certainty. It is easily reduced by 
means of carbon. 

Experiment 101. — Mix together about equal small quantities 
of arsenic oxide and finely powdered charcoal. Heat the mixture 
in a small dry tube of hard glass, closed at one end. The arsenic 
that is set free will be deposited on the walls of the tube in the 
form of a mirror, like that obtained in Experiment 100. 

Antimony, Sb {At, Wt, 120), occurs most frequently in 
combination with sulphur as the sulphide Sb2S3. It is a 
silver-white, metallic-looking substance. At ordinary 
temperatures it is not changed by contact with the air; 
but when heated to a sufficiently high temperature it takes 
fire and burns, forming the white oxide. 

Stibine, Antimoniuretted Hydrogen, SbH^. — This com- 
pound is made by the same method as that described 
under Arsenic. 

Experiment 102. — Make some stibine, using a solution of tar- 
tar emetic, a substance containing antimony. 

Its properties are much like fchose of arsine. It burns 
with a similar flame, and is decomposed in the same way. 

Experiment 103. — Introduce a piece of porcelain in the flame 
and notice the deposit or antimony spot. It is darker and more 
smoky than the arsenic spot. There are other differences in prop- 
erties, but they need not be treated of here. 

Boron, B {At, Wt, 11). — Boron may conyeniently be 
treated of in connection w^ith the members of the nitrogen 
family, as some of its properties suggest those of the 
members of that family. At the same time, it has 
peculiarities which distinguish it from these elemonts. 



lyo THE ELEMENTS OE CHEMISTRY. 

It occurs in nature in the form of horic, or horacic acid, 
in some hot springs, or as salts of this acid, particularly 
the sodium salt, or lorax. It is prepared by treating the 
oxide, B2O3 , at a very high temperature with sodium or 
aluminium. Under proper conditions it is obtained in the 
form of crystals, which are almost as hard as diamonds. 

Tetraboric Acid, H^B^O^ , is the form of boric acid from, 
which borax is derived. The formula of borax is 
Na^B^O, + lOH^O. 

The Cakbok Family: Carbo:n" akd Silicok. 

Occurrence of Silicon. — Carbon, as you have seen, occurs 
in every living thing. It is interesting to note that silicon, 
which in some respects resembles carbon in its chemical 
properties, is one of the most important constituents of 
the mineral or inorganic parts of the earth. It occurs 
chiefly in the form of the oxide, Si02, commonly called 
silica, or silicon dioxide; and in combination with oxygen 
and several of the common metals, particularly with 
sodium, potassium, aluminium, magnesium, and calcium, 
in the form of the silicates. 

Great Abundance of Silicon. — Next to oxygen silicon 
occurs in largest quantity in the earth. There are exten- 
sive mountain-ranges consisting almost entirely of silicon 
dioxide, SiOg , in the form known as quartz or quartzite. 
Other ranges are made up of silicates, which are com- 
pounds formed by a combination of silicon dioxide and 
bases. The clay of valleys, river-beds, etc., also contains 
silicon in large quantity, while the sand found so abun- 
dantly at the seashore is mostly silicon dioxide, SiO^. 



SILICON. 171 

The Element Silicon. — Unlike carbon, silicon is never 
found in nature in the uncombined state. It is an 
extremely difficult thing to decompose the oxide in such 
a way as to get the element. Under proper conditions 
silicon can be obtained in the form of crystals which have 
a gray color and are harder than glass. 

Silicides are compounds of silicon with other elements, 
as, for example, with carbon. These two elements com- 
bine forming an interesting compound, carlo n silicicle, 
CSi, which is manufactured on the large scale under the 
name of carhortmclum. It is made by heating a mixture 
of quartz sand, coke, and common salt in an electric 
furnace. It is a very stable substance, and is extremely 
hard, so that it is used as a substitute for emery. 

Silicic Acid. — There are several varieties of silicic acid, 
all of which are, however, derived from an acid of the 
formula H^SiO^, or normal silicic acid. When this is set 
free from its salts it loses water, and is changed to 
ordinary silicic acid, H.SiOg: 

H.SiO, = H,Si03 + H,0. 

When heated, this second form of silicic acid is converted 
into the dioxide SiO, : 

H,Si03 = SiO, + H,0. 

Silicon Dioxide, Silicic Anhydride, SiO^.— As already 
stated, this substance occurs very abundantly in nature 
and in many different forms. Quartz, or roch crystal, is 
pure crystallized silicon dioxide; qitartzite is a coarse- 
grained substance made up of small crystals of quartz, 
usually colored. Agate, amethyst, and carnelian are 



172 THE ELEMENTS OF CHEMISTRY. 

varieties of quartz colored by foreign substances. Silica 
also occurs in the stalks of some plants, giving them firm- 
ness, and in some cases making them so hard that they 
are valuable for polishing. 

Some of the more important silicates, as water-glass, 
glass, and the natural silicates, will be treated of farther 
on. 



CHAPTER XVIII. 

BASE-FORMING ELEMENTS— GENERAL CONSIDERA- 
TIONS. 

Distinction between Acid-forming and Base-forming Ele- 
ments. — The meaning of the name base-forming elements 
is that the compounds of these elements with hydrogen 
and oxygen are bases, or, in other words, have the power 
to neutralize acids and form salts. But the distinction 
between acid-forming and base-forming elements is not a 
sharp one, for the reason that there are some elements 
which form both acids and bases. 

Base-forming Elements. — The base-forming elements 
will be taken up in the following order: 

1. The Potassium Family^ the principal members of 
which are potassium and sodium. 

2. The Calcium Family, the principal members of 
which are calcium, barium, and strontium. 

3. The Magnesium Family,^ the principal members of 
which are magnesium and zinc. 

4. The Silver Family, consisting of silver, copper, and 
mercury. 

5. The Aluminium Family, of which aluminium is the 
only well-known member. 

173 



174 THE ELEMENTS OF CHEMISTRY. 

6. The L^on Family, consisting of iron, cobalt, and 
nickel. 

7. The Manganese Family, of which manganese is the 
only representative. There are some points of resemblance 
between manganese and the members of the chlorine 
family. 

8. The Clirommm Family, of which chromium is the 
principal member. There are some points of resemblance 
between chromium and the members of the sulphur 
family. 

9. The Bismuth Family, of which bismuth is the only 
representative. Between it and the members of the 
nitrogen family there are some points of resemblance. 

10. The Lead Family, the principal members of which 
are lead and tin. 

11. The Palladiitm Family, consisting of three rare 
elements. 

12. The Platinum Family, the principal members of 
which are platinum and gold. 

Large Number of Base-forming Elements. — You see that 
there are many more base-forming than acid-forming 
elements, and it is a serious undertaking to become 
thoroughly acquainted with all the elements included 
under this head. For the present it will be best to con- 
fine our attention to a few of the most important of the 
elements. 

Metallic Properties. — The base-forming elements are 
those which are usually called metals. The name metal 
is applied to those elements which have what is known as 
a metallic lustre, are opaque, and are good conductors of 
electricity. Gradually the name metal has come to mean 



BASE-FORMING ELEMENTS, 175 

an element that, lias the power to displace the hydrogen 
of acids and form salts. 

Classes of Metal Derivatives. — As the metals or base- 
forming elements all combine with oxygen, sul^ihur, 
chlorine, and also form salts with all acids, it follows that 
under each one there must be a large number of com- 
pounds. A thorough study of each metal would include 
the following subjects: 

1. Its Occurrence in Nature, — Under this head we 
should become acquainted with those natural compounds 
of the metals known as mineraJs, Those minerals from 
which the metals are extracted for practical purposes are 
called ores. 

2. Extraction of the Metals from their Ores, — The study 
of this subject is the object of metallurgy, 

3. The Properties of Metals. — As you will find, metals 
differ very markedly from one another. Some are light, 
floating on water, as potassium, sodium, etc. ; some are 
extremely heavy, as lead, platinum, etc. Some combine 
with oxygen with great energy; others form very unstable 
compounds with oxygen. Some form strong bases; others 
form weak bases. 

4. The Compounds of the Metals, — These may be con- 
veniently classified as : 

a. Compounds with chlorine, bromine, and iodine; or 
the chlorides, bromides, and iodides, 

h. Compounds with oxygen and with oxygen and hy- 
drogen ; or the oxides and hydroxides, 

c. Compounds with sulphur and with sulphur and 
hydrogen; or the sulphides and hydrosulp)hides. 



176 THE ELEMENTS OE CHEMISTRY, 

d. Compounds with nitric and nitrous acids; or the 
nitrates and nitrites. 

e. Compounds with the acids of chlorine; or the 
chlorates, clilorites, etc. 

/. Compounds with sulphuric and sulphurous acids; or 
the siili^lmtes and siilpliites. 

g. Compounds with carbonic acid; or the carlonates. 

h. Compounds with phosphoric acid; or the pliosphates. 

i. Compounds with silicic acid; or the silicates. 

j. Compounds with boric acid; or the borates. 

The acids of which the salts are derivatives are already 
known to you, and in dealing with the acids frequent 
reference has been made to the methods of making the 
salts, and to some of their most important properties. In 
what follows only those compounds will be treated of 
which well illustrate general principles, or which, owing 
to some familiar application, happen to be of special 
interest. 



CHAPTEK XIX. 

THE POTASSIUM FAMILY: POTASSIUM, SODIUM 
(AMMONIUM). 

Alkalies. — The members of this family are generally 
called metals of the alkalies, as the two best-known mem- 
bers are obtained from the alkalies, caustic potash and 
caustic soda, or potassium and sodium hydroxides. 

Potassium, K {At, Wt, 39). — This element is a con- 
stituent of many minerals, particularly of feld-S2Kir, which 
is a silicate of aluminium and potassium. 

In the Soil. — The natural decomposition of minerals 
containing potassium gives rise to the presence of this 
element in various forms of combination everywhere in the 
soil, and it is of the highest importance for plants, as 
they use it as part of their food. When vegetable material 
is burned the potassium remains behind, chiefly as potas- 
sium carbonate. When wood-ashes are treated with water 
the potassium carbonate dissolves, and it is obtained in an 
impure state by evaporating the solution. The substance 
thus obtained is called potash. 

Experiment 104. — Treat some wood-ashes with water. Filter 
off the solution, and examine it by means of red litmus-paper. 
Is the solution alkaline? Examine some potassium carbonate. — 
Does its solution act in the same way ? — Evaporate to dryness the 
solution obtained from the wood-ashes. Collect the dry residue 

J77 



178 THE ELEMENTS OF CHEMISTRY. 

and treat it in a test-tube with a little dilute hydrochloric acid. 
Is a gas given off ? Is it carbon dioxide ? 

Potassium is also found in the form of the chloride 
KCl, accompanying the chloride of sodium^ and as the 
nitrate in saltpetre. 

How Potassium is Prepared. — The metal was first pre- 
pared by the action of a powerful electric current on 
caustic potash, which had been considered as an element. 
It is now manufactured by the action of an electric current 
on potassium hydroxide, cyanide, or chloride. 

Properties. — It is a light substance that floats on water. 
Its freshly-cut surface has a bright metallic lustre, almost 
white; it acts upon water wdth great energy, causing the 
eyolution of hydrogen, w^iich burns, and the formation of 
j)otassium hydroxide. In consequence of its action on 
w^ater, potassium cannot be kept in the air. It is kept 
under some oil upon w^iich it does not act, as petroleum. 

Experiment 105. — Throw a small piece of potassium not larger 
than a pea upon water. What takes place ? What is the color 
of the flame ? What difference is there between the action of 
sodium and of potassium on water ? Is the solution after the 
action alkaline ? Why ? See note, Exp. 35. 

Compounds of Potassium. — The chief compounds of 
potassium are the iodide, KI; the hydroxide, or caustic 
potash, KOH; the nitrate, or saltpetre, KNO3; ^^® 
chlorate, KCIO3; and the carlonate, K2CO3. 

Potassium Iodide, KI, is made by treating caustic potash 
with iodine. The action is the same as that which takes 
place w^hen chlorine acts upon warm concentrated caustic 
potash. Both the iodide and iodate are formed : 

6K0H + 61 = 5KI + KIO3 + 3H,0. 



THE POTASSIUM FAMILY. 179 

By evaporating off the water and heating the residue, 
the iodate is decomposed into iodide and oxygen. 

Experiment 106. — Examine a bottle of crystallized potassium 
iodide. Taste a little. Dissolve some in water. Add some 
iodine to this solution. Does the iodine dissolve ? Heat a little. 
Does the substance contain Tvater of crystallization ? Treat a 
crystal or two with a few drops of concentrated sulphuric acid. 
What takes place ? To what is the appearance of violet vapors 
due ? See Experiment 88. 

Potassium iodide is extensively used in medicine and in 
photography. 

Potassium Hydroxide, KOH. — This well-known sub- 
stance, commonly called caustic potash, is j^repared by 
the action of an electric current on a concentrated solu- 
tion of potassium chloride (see page S3) : 

2KC1 + 2H,0 = 2K0H + R, + CI,. 

The hydroxide is a white brittle substance. In contact 
with the air it deliquesces [what does this mean ?] and 
absorbs carbon dioxide. It is a strong base. [What 
products are formed when it acts upon hydrochloric acid ? 
Upon nitric acid ? Upon sulphuric acid ? .How many 
salts can it form with sulphuric acid ? What are their 
formulas ?] 

Potassium Nitrate, KXO3. — The common name of this 
salt is saltpetre. Its occurrence in nature has already 
been referred to. When refuse animal matter is left to 
undergo decomposition in the presence of bases, nitrates 
are formed. 

Saltpetre Plantations. — Advantage is taken of the fact 
just mentioned for the purpose of preparing saltpetre 
artificially. Heaps of refuse matter from stables are 



i8o THE ELEMENTS OF CHEMISTRY, 

mixed with lime and kept moist, and then allowed to stand 
for a time. The nitrate which is formed is extracted with 
water, converted into potassium nitrate, and purified. 
Places where this process is carried on on the large scale 
are called saltfetre plantations. 

Properties. — Potassium nitrate crystallizes in long 
rhombic prisms which have a salty taste. It is easily 
soluble in water. 

Uses of Saltpetre. — It is used in making sulphuric acid 
[how?], and nitric acid [how?]. Its chief use is in the 
manufacture of gunpowder. 

Gunpowder. — The value of gunpowder is due to the fact 
that it explodes readily, the explosion being a chemical 
change accompanied by a sudden evolution of gases. 
When the powder is enclosed in a gun-barrel the gases in 
escaping drive the ball before them. Gunpowder has long 
been known, and has always been made of saltpetre^ char- 
coal, and sxilpliUT, When heated the saltpetre gives off 
oxygen and nitrogen; the oxygen combines with the char- 
coal, forming carbon dioxide, and the sulphur combines 
with the potassium, forming potassium sulphide. The 
reactions are represented in this equation : 

2KNO3 + 3C + S = SCO, + 2N + K,S. 

Gas. Gas. Solid. 

Experiment 107. — Mix together 15 grams potassium nitrate 
and 2.5 grams powdered charcoal. Set fire to the mass. 

Potassium Chlorate, KCIO3, has so frequently been 
referred to and used in earlier experiments that it is not 
necessary to say anything more about it now. 

Sodium, Na {^At, ^Tt, 23). — Sodium occurs yery widely 
distributed and in large quantities, principally as sodium 



THE POTASSIUM FAMILY, i8l 

chloride. It occurs also as sodium nitrate, and as the 
silicate in many minerals. Like potassium it is found 
everywhere in the soil, and is taken up by plants, especially 
by those which grow in the neighborhood of the sea and 
in the sea. 

Preparation of Sodium. — Sodium is made by the same 
method as that used for making potassium. 

Properties. — Its properties are very similar to those of 
potassium. It is light, floating on water, it has a bright 
metallic lustre, and is soft, like wax. It decomposes 
water, but not as actively as potassium. 

Sodium a Strong Reducing Agent.— Sodium has a strong 
attraction for oxygen, and is used in some chemical 
processes as a reducing agent, as, for example, in the 
preparation of aluminium. A compound of mercury and 
sodium, known as sodium amalgam, is used in some 
metallurgical operations connected with the extraction of 
gold and silver from their ores. 

- Compounds of Sodium. — The chief compounds of sodium 
are the chloride, NaCl; the hydroxide, or caustic soda, 
NaOH; the nitrate, or Chili saltpetre, NaNOg; the suh 
phate, Na^SO^; the carlonate, Na^COg; and the lorate, or 
borax, Na^B^O,. 

Sodium Chloride, NaCl. — This is the substance known 
by the name common salt. It occurs very widely dis- 
tributed, and, as it is easily soluble, much of the water 
which enters into the ocean contains some of it in solu- 
tion. Sea-water contains 2^ to 3 per cent af sodium 
chloride. 

How Salt is Obtained. — In some places salt is taken out 
of mines in the solid form; in others water is allowed to 



1 82 THE ELEMENTS OF CHEMISTRY, 

flow into the mines, and to remain for some time in con- 
tact with the salt, and the solution thus formed is drawn 
or pumped out of the mine and evaporated by appropriate 
methods. Salt is also obtained from the sea in hot 
countries. At high tide the water is dammed up, and 
the artificial ponds thus formed afterwards evaporate 
under the influence of the sun, leaving the salt behind. 

Properties. — Sodium chloride crystallizes in colorless 
and transparent cubes. Its taste is familiar to every one. 

Uses of Salt. — Salt is an extremely important article of 
food. It is necessary to the life of man as well as of many 
animals. It is found in all parts of the body. It is used 
to prevent decomposition of meats. Salt pork and salt 
fish are familiar to all. Salt is used as the starting-point 
in the preparation of all sodium compounds and of all 
chlorine compounds. 

[How are chlorine and hydrochloric acid obtained from 

it?] 

Sodium Hydroxide, NaOH. — This is commonly called 
caustic soda. It can be prepared in the same way as 
potassium hydroxide. Its properties are very similar to 
those of caustic potash. 

Sodium Nitrate, JSTaNOg. — This is the salt which has 
been repeatedly referred to by the name of Chili saltpetre. 
It occurs in very large quantities, and is the chief source 
of nitric acid. It is cheaper than potassium nitrate, but 
cannot be substituted for it in the manufacture of gun- 
powder, because it becomes moist in the air. It is con- 
verted into potassium nitrate by treating its solution with 
potassium chloride : 

NaNO^ -f KCl = KNO3 + XaCl. 



THE POTASSIUM FAMILY, 183 

The potassium nitrate is separated from the sodium 
chloride by crystallization. 

Sodium Sulphate, ]Sra2S0^ + lOH^O. — The common name 
of this substance is Glauber^s salt. It is manufactured in 
large quantities by treating sodium chloride with sul- 
phuric acid : 

2NaCl + H^SO, = 2HC1 + Na^SO,; 

and by the action of magnesium sulphate on sodium 
chloride : 

2NaCl + MgSO, = Na^SO, + MgCl,. 

It crystallizes in large, colorless, monoclinic prisms, 
containing 10 molecules of water of crystallization, 
Na^SO^ + lOHgO. It loses water when left in contact 
with the air. 

It is extensively used in the manufacture of glass. 

Sodium Carbonate, Na^CO^ + lOHgO. — This salt, com- 
monly called soda, is one of the most important of manu- 
factured chemical substances. The mere mention of the 
fact that it is essential to the manufacture of glass and 
soap will give an idea of its importance. It is found in 
the ashes of sea-plants, just as potassium carbonate is 
found in the ashes of land-plants. Formerly it was 
obtained from this source. Now, howeyer, we are not 
dependent upon sea-plants for our supply, as two methods 
haye been deyised for preparing it from sodium chloride, 
with which the earth is so abundantly supplied. 

Manufacture of Soda from Sodium Chloride. — During the 
French Keyolution the supply of soda was cut off from 
France, and the goyernment therefore offered a large prize 



1 84 THE ELEMENTS OF CHEMISTRY. 

for a method of making it from common salt. A method 
was devised by Leblanc which has been used very exten- 
sively ever since. 

Leblanc's Method for Making Soda. — This depends upon 
four reactions : 

1st. The sodium chloride is converted into sodium sul- 
phate by treating it with sulphuric acid : 

2NaCl -f H^SO, = Na^SO, + 2HC1. 

2d. The sodium sulphate thus obtained is heated with 
charcoal, which reduces it to sodium sulphide, Na^S: 

Na^SO, + 40 =: Na,S + 4C0. 

3d. The sodium sulphide is heated with calcium car- 
bonate, when sodium carbonate and calcium sulphide are 
formed : 

■ Na^S + CaC03 = Na,C03 + CaS. 

4th. If lime is present in the last reaction, it forms an 
insoluble compound with calcium sulphide. By treating 
the product of the reaction with water the sodium car- 
bonate alone dissolves. 

In practice the sodium sulphate is mixed with charcoal 
and calcium carbonate and the mixture heated. 

The Solvay or Ammonia Method. — Another method has 
recently come into great prominence, threatening to drive 
out the Leblanc method completely. This is the Solvay, 
or the ammonia, method. This depends upon the fact 
that the salt, HNaCOg, is comparatively difficultly soluble 
in water and is therefore precipitated from a solution of 
common salt by the addition of the easily soluble acid 
ammonium carbonate. 



THE POTASSIUM FAMILY. 185 

Properties. — Sodium carbonate crystallizes in large 
prisms with 10 molecules of water of crystallization. The 
crystals are efflorescent. 

Mono-Bodium Carbonate, HNaCOg, or licarlonate of 
soda, is made from sodium carbonate by passing carbon 
dioxide into it : 

Na^CO, + CO, + H,0 = 2HNaC03. 

This substance is one of the constituents of lahing- 
powders which are used for raising bread. Seidlitz 
powders consist of the bicarbonate and cream of tartar 
mixed together. When water is added to the mixture, 
carbon dioxide is given off, as the cream of tartar is an 
acid salt, acid potassium tartrate, KHC^H^Og, and 
Rochelle salt is left in solution. This is the potassium 
and sodium salt of tartaric acid, of the composition 
KNaC,H,0,. 

Disodium Phosphate, Na^HPO, + 12H,0.— This is the 
common form of sodium phosphate. 

Sodium Borate, Borax, ISTa^B^O^ + lOH^O. — This salt is 
found in several lakes in Asia, and in this country in Clear 
Lake, Nevada. It is also manufactured by neutralizing 
the boric acid found in Tuscany. When heated, borax 
puffs up, and at red heat melts, forming a transparent, 
colorless liquid. This is the dry substance, Na2B^0^. 
Molten borax has the power to dissolve the oxides of the 
metals, and forms colored glasses with some of them. In 
soldering it is necessary that the metals should be clean 
and bright. To secure this a little molten borax is put 
on the surfaces which are to be united. Borax is an 
antiseptic; that is to say, it prevents the decomposition 
of organic substances. 



i86 THE ELEMENTS OF CHEMISTRY. 

Water-glass. — Silicon dioxide, or silica, SiO^, dissolves 
by continued boiling with caustic soda or potash, and 
sodium or potassium silicate is thus formed : 

SiO, + 2NaOH = Na^SiOg + H,0. 

These salts are soluble in water, and are known as 
water-glass. Water-glass is used in making artificial 
stone, and for the purpose of protecting certain stones 
from the action of the weather. 

Ammonium Salts. — When the gas ammonia, NHg, or its 
solution in water, is brought together with acids, salts are 
formed. Thus ammonia and hydrochloric acid give a salt 
of the composition NH^Cl; ammonia and nitric acid give 
NH^NOg; ammonia and sulphuric acid give (NHJ^SO^. 
The salts are formed according to the following equations: 

NH3 +HC1 =:NH,C1; 
NH3 +HN03 = NH,N03; 
2NH3 +H,SO, ^ (NHJ^SO,. 

The salts thus formed are much like the salts of sodium 
and potassium. They can be understood best by assuming 
that in them the part represented by NH^ acts the part of 
the metal in metallic salts. 

It is called ammonium, and the salts are called am- 
yaonium salts. Ammonium has never been obtained in 
the uncombined state, as instead of it ammonia and 
hydrogen are always formed. 

Experiment 108. — Place near each other two vessels, one con- 
taining a little strong hydrochloric acid, and the other a little 
strong ammonia. Explain what you see. 

Ammonium Chloride, NH^Cl. — This salt is sometimes 
called sal-ammoniac. When heated it is converted into 



THE POTASSIUM FAMILY. 187 

vapor without melting, and with very slight decomposi- 
tion. 

Experiment 109. — On a piece of platinum-foil or porcelain 
heat a little ammonium chloride. What is the result ? 

[What takes place when ammonium chloride is treated 
with caustic soda ? With lime ?] 

Ammonium Sulphide, (^11^28. — This salt, which is 
made by treating ammonia with hydrogen sulphide, is 
extensively used in making chemical analyses. 

Relations between the Atomic Weights of the Alkali 
Metals. — The atomic weight of lithium, which is a metal 
belonging to the potassium family, is 7. Between this 
and the atomic weights of sodium, 23, and potassium, 39, 
exist relations similar to those which exist between the 
atomic weights of chlorine, bromine, and iodine; and of 
sulphur, selenium, and tellurium. [What is this rela- 
tion ?] 

Flame Reactions. — When a piece of clean platinum wire 
is held for some time in the flame of the Bunsen burner, 
it then imparts no color to the flame. If now a small 
piece of sodium carbonate or any other salt of sodium be 
put on it, the flame is colored intensely yellow. All 
sodium compounds have this power, and hence the chemist 
makes use of the fact for the purpose of detecting the 
presence of sodium. Similarly, potassium compounds 
color the flame violet. 

Experiment 110. — Prepare some pieces of platinum wire, 8 to 
10 cm. long, with a small loop on the end. After thoroughly 
cleaning them, insert one in a little sodium carbonate, and notice 
the color it gives to the flame. Try another with potassium car- 
bonate. 



1 88 THE ELEMENTS OF CHEMISTRY, 

To Separate Two or More Colors. — While it is an easy 
matter to recognize potassium alone, or sodium alone, it 
is not so easy to do so when they are together in the same 
compound. The intense yellow caused by the sodium 
completely masks the more delicate violet caused by the 
potassium, so that the latter cannot be seen by the unaided 
eye. In this particular case we can get over the difficulty 
by letting the light pass through a blue glass, or a thin 
vessel filled with a solution of indigo. The yellow light 
is thus cut off, while the violet light passes through and 
can be recognized. 

The Prism and the Spectrum. — A better method for 
detecting what a light consists of is by means of a prism. 
Lights of different colors are turned out of their course to 
different extents when passed through a prism, as is seen 
in the case of sunlight. A narrow beam of white light 
passing in emerges as a band of various colors, called its 
spectrum. It is thus seen that white light is made of 
different-colored lights. Similarly, we can determine 
what any light is composed of. Every light has its char- 
acteristic spectrum. The light produced by burning 
sodium, or by introducing a sodium compound in a color- 
less flame, has a spectrum consisting of a narrow yellow 
line or two lines very near together. The spectrum of 
potassium consists mainly of two lines, one red and one 
violet. Further, these lines always occupy definite posi- 
tions relatively to one another, so that, in looking through 
a prism at the light caused by potassium and sodium, the 
yellow line of sodium is seen in its position, and the two 
potassium lines in their positions. 



THE POTASSIUM FAMILY, 189 

The Spectroscope. — The instrument used for the purpose 
of examining the spectra of different lights is called the 
spectroscope. It consists essentially of a prism and two 
tubes. Through one of the tubes a narrow beam of the 
light to be examined is allowed to pass so as to strike on 
the prism. The light emerges from the other side of the 
prism, and is observed through the other tube, which is 
provided with lenses for the purpose of magnifying the 
spectrum. By means of the spectroscope it is possible to 
detect the minutest quantities of some elements, and, 
since it was devised, several new elements have been dis- 
covered through its aid, as, for example, caBsium, rubidium, 
thallium, indium, and gallium. 

Discovery of Helium by the Aid of the Spectroscope. — An 
interesting case of the use of the spectroscope is that of 
helium. A certain yellow line is characteristic in the 
spectrum of this element. It was first observed in the 
solar chromosphere and protuberances. More than twenty- 
five years later it was found in the gases given off from 
certain rare minerals. It has since been studied with 
some care. Its atomic weight is 4, 



CHAPTEE XX. 

THE CALCIUM FAMILY: CALCIUM, BARIUM, 
STRONTIUM. 

Calcium, Ca {At. Wt, 40). — This is the principal mem- 
ber of the family. It is widely distributed in nature and 
in enormous quantities; principally as carbonate, CaCOg, 
in the form of limestone, marble, and chalk; as sulphate, 
CaSO^, in the form of gypsum; as phosphate, Ca3(POj2> 
in phosphorite and apatite; as fluoride, CaFg, in fluor spar. 

The element is not easily made. It acts upon water 
just as sodium and potassium do. 

Compounds of Calcium. — The principal compounds of 
calcium with which we have to deal are the chloride, 
CaCl2; the oxide, or quicklime, CaO; the hydroxide, or 
slaked lime, Oa(OH)2; the carMde, Qj^Q>^', the hypochlorite, 
Ca(0Cl)2; the cario7iate, CaCO,; the sulphate, CaSO/, the 
phosphate, Ca3(P0Jj and the silicates, in the form of 
glass. 

Calcium Chloride, CaCl2. — The property which gives this 
salt its yalue is its power to absorb water. It is used as a 
drying agent. Gases are passed through it for the pur- 
pose of drying them, and it is also placed in vessels in 
which it is necessary that the atmosphere should be kept 
dry. 

190 



THE CALCIUM FAMILY. I91 

Experiment 111. — Dissolve 10 to 20 grams of limestone or 
marble in ordinary hydrochloric acid. Evaporate to dryness. 
Expose a few pieces of the residue to the air. — Does it become 
moist ? In what experiments has calcium chloride been used, 
and for what purposes ? What would happen if sulphuric acid 
were added to calcium chloride ? Try it. Explain what takes 
place. Is the residue soluble or insoluble in water ? 

Calcium Oxide, CaO. — This is the substance commonly 

called lime. It is made by heating calcium carbonate, 

which is decomposed into lime and carbon dioxide : 

CaCOg = CaO + CO,. 

Limekilns are large furnaces in which limestone and 
other forms of calcium carbonate are heated and converted 
into lime. 

Lime is a white substance which does not melt except 
in the electric furnace. When heated in the flame of the 
oxyhydrogen blowpipe, it gives forth an intense light, as 
any other infusible substance would under the same cir- 
cumstances. When exposed to the air, it attracts moisture 
and carbon dioxide and is thus converted into the car- 
bonate. This change is called air-slaking y and lime thus 
changed is said to be air-slaked. 

Calcium Hydroxide, Ca(0H)2. — When calcium oxide or 
quicklime is treated with water it becomes hot and crum- 
bles to a fine powder. The substance which is formed in 
this operation is somewhat soluble in water, the solution 
being known as lime- neater. 

Slaking. — The action that takes place when lime is 
treated with water is called slaking. It is represented by 
the equation 

CaO + H,0 = Ca(0H)2. 

The oxide is converted into the hydroxide or hydrate. 



192 THE ELEMENTS OF CHEMISTRY. 

Experiment 112. — To 40 or 50 grams good quicklime add 
100 c.c. Water. What takes place ? Afterwards dilute to 2 to 3 
litres and put the whole in a wide-stoppered bottle. The un- 
dissolved lime will settle to the bottom, and in the course of 
some hours the solution above will become clear. Carefully pour 
off some of the clear solution. What takes place when some of 
the solution is exposed to the air ? When the gases from the 
lungs are passed through it ? When carbon dioxide is passed 
through it? What takes place when dilute sulphuric acid is 
added to lime-water? Is calcium sulphate difficultly or easily 
soluble in water ? Has lime-water an alkaline reaction ? What 
reaction would you expect to take place between lime and nitric 
acid? 

Calcium Carbide, CaOg. — This compound is easily formed 
by heating lime and coke together in the form of powder 
in an electric furnace, when the reaction represented below 
takes place : 

CaO + 30 =: CaC, + CO. 

It is a crystallized substance. With water it gives acety- 
lene and lime. (See Acetylene.) 

Calcium Hypochlorite, Ca(0Cl)2, has already been 
treated of sufficiently under the head of Chlorine. It need 
only be repeated that the form in which chlorine is trans- 
ported is ^^hleaching-powder^' or ''chloride of limeJ^ 
This is a compound containing calcium hypochlorite and 
calcium chloride, Ca(0Cl)2 + CaCl^, which is made by 
passing chlorine into slaked lime : 

2Pa(0H), + 4C1 = Ca(OCl), -f CaOl, + 2H,0. 

Bleaching-powder. 

How Bleaching-powder Gives up Chlorine. — Bleaching- 
powder gives up its chlorine by simple exposure to the air 
in consequence of the action of the carbon dioxide. The 
addition of an acid causes a rapid evolution of chlorine. 



THE CALCIUM FAMILY. 1 93 

Calcium Carbonate, CaCOg. — This salt occurs in nature 
in the well-known forms calc-spar, limestone, marble, and 
chalk. The variety of calc-spar found in Iceland, and 
known as Iceland spar, is particularly pure calcium car- 
bonate. The salt also forms the principal part of oyster- 
shells, coral, etc. In some caves water containing calcium 
carbonate in solution drips down, and the salt is deposited 
in the solid form from the solution because the excess of 
carbon dioxide that holds the carbonate in solution is 
given off (see page 128). Thus hanging pieces, shaped 
like icicles are formed, and below them reaching up 
from the bottom are similar pieces with the pointed 
ends upwards. Those which hang down from above 
are called stalactites; those on the bottom are called 
stalagmites. 

Calcium Sulphate, Gypsum, CaSO^ + 2H2O. — Gypsum is 
the principal variety of calcium sulphate. When heated 
it loses part of its water of crystallization and forms a 
powder called plaster of Paris^ which has the power of 
taking up water and forming a solid substance. The pro- 
cess of solidification is known as ^^ setting.''^ Plaster of 
Paris is largely used in making casts. 

Experiment 113.— Heat some powdered gypsum to about 180° 
in an air-bath. Examine what is left and see whether it will be- 
come solid when mixed with a little water so as to form a paste. 
See whether gypsum itself will act in the same way. 

Permanent Hardness of Water. — Calcium sulphate is 
somewhat soluble in water. A natural water containing 
either gypsum or calcium carbonate is called a hard ivater. 
The hardness caused by calcium carbonate is remedied by 
boilmg the water, and is, therefore, called temporary 



194 THE ELEMENTS OF CHEMISTRY. 

hardness, while that which is caused by gypsum is not 
remedied by boiling and is therefore called permanent 
hardness. Why the water is called hard will be explained 
when the subject of soap is treated. 

How to Improve Hard Water. — Water that holds calcium 
carbonate in solution can be made soft by adding a little 
lime to it. This forms insoluble calcium carbonate with 
the carbon dioxide^ and, as soon as the carbon dioxide is 
removed, the calcium carbonate in solution is precipitated. 
If the hardness is caused by calcium sulphate the addition 
of a little carbonate of soda will precipitate the calcium as 
calcium carbonate, and sodium sulphate will be left in 
solution : 

CaSO, + Na,C03 = CaC03 + Na^SO,. 

[Try these reactions.] 

Gypsum Valuable as a Fertilizer. — The addition of 
gypsum to a soil increases its fertility, and it is therefore 
frequently used by farmers to increase their crops. 

Calcium Phosphate, Ca3(POj2- — The normal phosphate 
in which calcium is substituted for all the hydrogen of 
phosphoric acid is found in nature as phosphorite, and in 
combination with calcium fluoride or chloride as apatite. 
Further, it is the chief earthy constituent of bones, and is 
found in large quantity in bone-ash. 

Calcium Phosphate as a Fertilizer. — Plants need phos- 
phoric acid for their growth, and hence it must b^- present 
in the soil if the plants are to flourish. Ordinary normal 
calcium phosphate is not soluble, and is therefore not 
easily taken up by the plants. It can be rendered soluble 
by adding sulphuric acid to it, and then it is readily used 
by the plants. 



THE CALCIUM FAMILY. 195 

Superphosphate of Lime. — Normal calcium phosphate 
that has been treated with a certain proportion of sulphuric 
acid forms the valuable artificial fertilizer known as stiper- 
pliospliate of lime. This is a mixture of the phosphate 
Ca(H2POj2 and calcium sulphate formed thus: 

Ca3(P0J, + 2H,S0, = 2CaS0, + Ca(H,POJ,. 

Superphosphate of lime. 

Mortar. — Mortar is made of slaked lime and sand. 
When this mixture is exposed to the air, calcium carbonate 
is slowly formed, and the mass becomes extremely hard. 
The water contained in the mortar soon passes off, but 
nevertheless freshly-plastered rooms remain moist for a 
considerable length of time. This is due to the fact that 
a reaction continues to take place between the carbon 
dioxide and calcium hydroxide in which calcium carbonate 
and water are formed, 

., Ca(OH), + CO, = CaC03 + H,0, 

and it is the water thus set free which keeps the air moist. 
The complete conversion of the lime into carbonate 
requires a long time, because the carbonate that is formed 
on the surface tends to protect the lime in the interior. 
The hardening can be hastened by keeping up fires of coke 
or charcoal and allowing the products of combustion to 
escape into the rooms. 

Glass. — Common glass is a silicate of calcium and 
sodium, made by melting together sand (silicon dioxide, 
SiOJ with lime, or calcium carbonate, and sodium car- 
bonate. When potassium carbonate is used instead of 
sodium carbonate the glass is more difficultly fusible. 



196 THE ELEMENTS OF CHEMISTRY, 

Bohemian glass, which is so extensively used in the manu- 
facture of chemical apparatus, is a silicate of calcium and 
potassium. Flint-glass, which is especially valuable for 
the manufacture of optical instruments, contains lead 
instead of calcium. It melts much more readily than 
calcium glass. 

Colored Glass. — Colors are given to glass by putting in 
the fused mass small quantities of various substances. 
Thus a cobalt compound makes glass blue; copper and 
chromium make it green; one of the oxides of copper 
makes it red, etc. 

Compounds of Barium and Strontium. — These closely 
resemble those of calcium. Barium forms an oxide, BaO, 
corresponding to lime, and also another one known as 
barium dioxide, BaOg. This is formed by passing oxygen 
or air over barium oxide heated to a dull red heat. At a 
higher temperature it gives off the oxygen. These facts 
are taken advantage of for the purpose of extracting 
oxygen from the air. 

Barium Dioxide Used in Making Hydrogen Dioxide. — 
Barium dioxide has already been referred to in describing 
the preparation of hydrogen dioxide, H2O2. When it is 
treated with sulphuric acid this reaction takes place : 

BaO, + H^SO, = H,0, + BaSO,. 

When it is treated with hydrochloric acid hydrogen dioxide 
is also formed, thus : 

BaO, + 2H01 = H^O, + BaCl,. 

[Compare this with the reaction which takes place 
when hydrochloric acid acts upon manganese dioxide.] 



THE CALCIUM FAMILY. 197 

Flame Reactions. — Calcium compounds color the flame 
reddish-yellow; strontium compounds, intense red; and 
barium compounds, yellowish-green. They are frequently 
used for the purpose of producing colored lights. 

Relations between the Atomic Weights. — The atomic 
weight of calcium is 40, that of strontium 87.5, and that 
of barium 137. [Why is this fact of special interest ?] 



CHAPTER XXI. 

THE MAGNESIUM FAMILY: MAGNESIUM, ZINC, 
CADMIUM. 

THE COPPER FAMILY: COPPER, MERCURY, SILVER. 

Magnesium, Mg {At, Wt, 24). — Magnesium occurs very 
widely distributed in nature, and in considerable quan- 
tities. Among the important magnesium minerals are 
magnesite, which is the carbonate, MgCOg; dolomite, a 
carbonate of magnesium and calcium; soapstone, serpen- 
tine^ and meerscliaum^ which are essentially silicates of 
magnesium. Further, there are many well-known min- 
erals that contain magnesium, as asbestos and Jiornhlende. 
The element is also found in solution in many spring- 
waters in the form of the sulphate, which is known as 
Epsom salt. 

Preparation of Magnesium. — It is prepared by electroly- 
sis of dehydrated carnallite, KMgClg. This is melted in an 
iron crtTcible. One pole of the battery is a piece of 
carbon, the other is the crucible itself. 

Properties. — It is a silver-white metal with a high lustre. 
In the air it changes slowly, but it gradually becomes 
covered with a layer of the oxide. It burns with a bright 
flame, forming the white oxide and some nitride, Mg^K^. 

198 



THE MAGNESIUM FAMILY, 199 

At ordinary temperatures magnesium does not decompose 
water; at 100° it decomposes it slowly. [Compare mag- 
nesium with potassium and sodium in this respect.] 

Magnesium Oxide, MgO. — This compound is commonly 
called magnesia. A fine white variety is made by heating 
precipitated magnesium carbonate; this is called magnesia 
usta. It is very difficultly soluble in water, forming with 
it magnesium hydroxide, Mg(0H)2, which is practically 
insoluble in water. [What difference is there between 
magnesium and calcium in this respect ?] 

Zinc, Zn {At, Wt, 65), — Zinc occurs in nature in com- 
bination as the carbonate, or calami7ie, ZnCOg, as the 
silicate, and as the sulphide, or zinc blende, ZnS. 

Preparation of Zinc, — It is prepared by mixing the oxide 
with charcoal and heating in earthenware retorts. The 
metal, being volatile, passes over and is condensed. 

Properties of Zinc. — Zinc has very different properties at 
different temperatures. At ordinary temperatures it is 
quite brittle*, at 100-150° it can be rolled out in sheets, 
but above 200° it becomes brittle again. In dry air it does 
not change. When heated in the air it takes fire, and 
burns with a bluish flame, forming zinc oxide. It dis- 
solves in all the common acids, usually with an escape of 
hydrogen. 

Uses. — It is used very largely in making batteries. Iron 
covered with a layer of zinc is known as galvanized iron. 
Zinc plates covered with a layer of zinc amalgam, formed 
by applying mercury, are used in galvanic batteries. Zinc 
is one of the constituents of brass, the other being copper. 
German silver consists of brass to which some nickel has 
been added. 



200 THE ELEMENTS OF CHEMISTRY, 

Zinc Oxide, ZnO, is obtained as Flores zinci by burning 
zinc, and by heating the carbonate or nitrate of zinc. It 
turns yellow when heated, but becomes white again on 
cooling. 

Experiment 114. — In a furnace, or in a hot stove fire, heat a 
small sand crucible to a bright red heat. Throw into it pieces of 
zinc. If the temperature is high enough the zinc will boil and 
the vapor will burn with a bright light, and dense white fumes of 
the oxide will be formed. — Heat a small piece of zinc or charcoal 
in the oxidizing flame of the blowpipe. The white fumes of zinc 
oxide {philosopher's wool) will be seen, and the charcoal will be 
covered with a film that is yellow while hot, but becomes white 
on cooling. 

Zinc oxide is used as a constituent of paint under the 
name zinc-ioMte, White lead turns black quite readily. 
Zinc-white does not. 

Zinc Sulphate, ZnSO^ + 7H2O. — The common name of 
this salt is ^ohite vitriol. It is obtained on the large scale 
by heating zinc sulphide in contact with the air. Under 
these circumstances the sulphide is oxidized : 
ZnS + 40 = ZnSO,. 

This operation is known as roasting. By roasting zinc 

sulphide at a higher temperature it is converted into zinc 

oxide : 

ZnS + 30 1= ZnO + SO^. 

Zinc sulphate is also formed in large quantities in gal- 
vanic batteries and in the preparation of hydrogen. 

Copper, Cu {At. Wt, 63.1). — Copper occurs in nature in 
the uncombined or native state in large quantities in the 
neighborhood of Lake Superior, United States, and in 
Chili. It also occurs in combination with oxygen as riily 
copper, which is the oxide, CU2O; and with sulphur and 
iron in copper pyrites^ CuFeSj. 



THE COPPER FAMILY. 201 

Preparation of Copper. — Copper is obtained from the 
oxide by heating it with charcoal. [This reduction lias 
been ilhistrated under the head of carbon (see Experiment 
70)]. It is also obtained from the sulphides. The chem- 
ical changes involved are comparatively complicated. It 
is also made electrolytically. 

Properties. — Copper is a hard metal of a reddish color 
and metallic lustre. In dry air it does not change, but in 
moist air it gradually becomes covered with a green layer 
of a carbonate of copper. Mtric acid dissolves it, copper 
nitrate, Cu(E'03)2, being formed, and oxides of nitrogen 
evolved [explain the reaction] ; hydrochloric acid does not 
act upon it; sulphuric acid acts when heated with the 
metal; the sulphate, CuSO^ , is formed and sulphur dioxide 
given off. Copper does not decompose water, even when 
water vapor is passed over the metal heated to redness. 
[Compare with the conduct of the members of the potas- 
sium, calcium, and magnesium families. 

Copper-plating. — Copper is precipitated from solutions 

of its salts by zinc, iron, and some other metals, and by 

an electric current. 

Experiment 115. — Into a neutral solution of copper sulphate 
insert a bright strip of zinc. The zinc will become covered with 
a layer of copper, and zinc will pass into solution as zinc sul- 
phate. The zinc displaces the copper in this case, as it displaces 
hydrogen from sulphuric acid : 

Zn + CUSO4 = ZnS04 + Cu ; 

Zn + H2SO4 = ZnS04 + H^. 

Perform a similar experiment, using a bright strip of sheet- 
iron instead of zinc. [What is the result ?] 

The deposition of metallic copper from solutions of its 
salts is extensively used in copyer-plating. The object to 
be covered with copper is hung in a solution of copper 



202 THE ELEMENTS OF CHEMISTRY. 

sulphate and connected with one pole of a galvanic battery, 
the other pole being also in the solution. Decomposition 
takes place, and a layer of copper is deposited on the 
object. 

Alloys of Copper. — Mixtures of metals made by melting 
them together are called alloys. Brass is an alloy con- 
sisting of about 1 part of zinc and 2 parts of copper. 
Bell-metal and bronze are alloys of copper and tin. 

Copper Forms Two Series of Salts. — Copper has the 
power to form two distinct series of compounds, of which 
the following are examples : 

CuCl, CuCl,; 
CuBr, CuBr^; 

Cu^O, CuO. 

Those which belong to the first class, corresponding to the 
chloride, CuCl, are called cuprous compounds. Thus, 
CuCl is cuprous chloride; Cufi, cuprous oxidCy etc. On 
the other hand, compounds of the second class are called 
cupric com2)Ounds. Thus, CUCI2 is cupric chloride; CuO, 
cupric oxide, etc. Mercury, iron, and some other metals 
also form two series of compounds which differ from each 
other in much the same way. 

Cuprous Oxide, Cu^O, is found in nature as ruly copj^er^ 
and is formed when copper is heated in contact with the 
air. It is a bright-red, compound insoluble in water. 

Cupric Oxide, CuO, is obtained by heating copper to red- 
ness in contact with the air, or by heating the nitrate. It 
is also formed when caustic soda or potash is added to a 
boiling-hot solution of a copper salt. If the solution is 
cold, blue cupric hydroxide, Cu(0H)2, is precipitated, but 



THE COPPER FAMILY, 203 

this easily loses water, and is converted into the oxide, 
CuO, which is black, particularly if the solution is heated. 
The reactions which take place are : 

CuSO, + 2XaOH = Cu(OH), + Na^SO,, and 
Cu(OH), = CuO + H,0. 

Experiment 116.— Add a dilute solution of caustic soda or 
potash to a small quantity of a dilute cold solution of copper 
sulphate in a test-tube. After noticing the appearance of the 
precipitate first formed, heat. What change takes place ? — Add 
caustic soda in the same way to a hot solution of copper sulphate. 

Copper Sulphate, CuSO^ -f SH^O. This salt is manufac- 
tured on a large scale, and is commonly known by the 
name ^^blue yitriol.^^ [What salt is called ^^ white 
vitriol '^ ?] It forms large blue crystals, which, when 
heated, lose water and become colorless. The colorless 
substance becomes blue again in contact with water. It 
is used in galvanic batteries, in copper-plating, and as a 
remedy for the pest of grape-vines, phylloxera. 

Mercury, Hg [At, Wt, 200). — Mercury occurs in the 
uncombined state as drops enclosed in rocks, though 
principally in combination with sulphur as cinnabar, HgS. 
It is obtained by roasting cinnabar, when vapors of 
mercury and sulphur dioxide are given off. The mercury 
is then condensed in appropriate vessels. It is a silver- 
white inetal of a high lustre. At ordinary temperatures 
it is liquid, though it becomes solid at — 39°. 5. It does 
not change in the air at ordinary temperatures. It is 
insoluble in hydrochloric acid and cold sulphuric acid. 
[Try each.] It dissolves in hot concentrated sulphuric 
acid, and is easily soluble in nitric acid. [Try each.] 
The vapor of mercury is very poisonous. 



2 04 THE ELEMENTS OF CHEMISTRY. . 

Amalgams. — With other metals mercury forms alloys 
called amalgams. In ordinary galvanic batteries the zinc 
plates are treated with mercury, and thus covered with a 
layer of zinc amalgam which protects them from the 
action of the acids used. 

Mercuric Oxide, HgO, is the red substance that was used 
in one of the first experiments for the purpose of prepar- 
ing oxygen. It is formed when mercury is heated for 
some time near its boiling-point in contact with the air, 
and is made by heating the nitrate. 

Mercurous Chloride, HgCl, is commonly known by the 
name calomel. It is precij^itated when a soluble chloride 
or hydrochloric acid is added to a solution of any mercur- 
ous salt. It is manufactured by subliming an intimate 
mixture of mercuric chloride and mercury: 

HgCl, + Hg = 2HgCl. 

It is a white substance, insoluble in water, which finds 
extensive application in medicine. 

Mercuric Chloride, IIgCl2, commonly called corrosive 
suUimate^ is manufactured on the large scale by subliming 
an intimate mixture of mercuric sulphate and common 
salt: 

HgSO, + 2NaCl =: Na^SO, + HgCl,. 

It is a white substance, soluble in water. It is extremely 
poisonous, and prevents the decay of organic substances. 
It is used as an antiseptic in surgery. 

Silver, Ag {At, Wt, 107). — Silver occurs in the uncom- 
bined state or native; in combination with sulphur; and 
with sulphur and other metals. Small quantities of silver 
sulphide are found in almost all varieties of galenite or lead 



THE COPPER FAMILY. 205 

sulphide. It occurs more rarely as the chloride, bromide, 
and iodide. 

Extraction of Silver from its Ores. — Much of the silver 
used is obtained from galenite. This mineral is treated 
so as to effect the separation of the lead (see Lead), and 
the silver is separated from sulphur at the same time. 
But it is dissolved in a large quantity of lead, and the 
problem which presents itself to the metallurgist is how 
to separate the small quantity of silver from the large 
quantity of lead. 

PaUinson's Process, — The separation of the silver from 
the lead is accomplished by a process invented by Pattin- 
son. It consists in melting the mixture and allowing it to 
cool until crystals appear. These are nearly pure lead. 
They are dipped out and the liquid left is again treated in 
the same way. By this means there is finally obtained a 
product which is rich in silver, but which still contains 
some lead. This is heated in appropriate vessels in con- 
tact with the air, when the lead is oxidized, while the 
silver remains in the metallic state. This last process is 
called cupellaiion. This process has been superseded by 
the 

Zinc Method, or Parker^s Method. — This consists in 
treating the molten alloy with zinc, which takes up all the 
silver. The alloy of zinc and silver thus formed is 
removed, and afterwards treated with superheated steam, 
by which the zinc is oxidized and the silver left un- 
changed. 

Amalgamation Process. — Some ores of silver are treated 
in another way, known as the amalgamation process. The 
ores are mixed with common salt and roasted, when the 



2o6 THE ELEMENTS OE CHEMISTRY. 

silver is obtained in the form of the chloride. The mass 
is then treated with iron and water, when this reaction 
takes place: 

2AgCl + Fe = FeCl, + 2Ag. 

The mass is next treated with mercury, which forms an 
amalgam with the silver. When this amalgam is taken 
out, dried and heated, the mercury passes over, while the 
silver remains behind. 

Properties of Silver. — Silver is a white metal with a high 
lustre. It is not acted upon by air, oxygen, or water at 
ordinary temperatures. Sulphur acts readily upon it, 
causing it to blacken superficially, the black coating being 
silver sulphide. Silver coins and other articles carried in 
the pockets are apt to become tarnished in consequence 
of the presence of small quantities of sulphur in the 
perspiration. 

Alloys of Silver. — The silver which is used for coins and 
most other purposes is an alloy with copper, the pure 
metal being too soft. The alloy usually contains from 7|- 
to 10 per cent of copper. 

Silver-plating. — Objects are covered with silver mostly 
by connecting them with one pole of an electric battery 
and placing them in a bath containing a silver salt in 
solution, in which the other pole of the battery is also 
inserted. Glass is covered with silver by putting it into 
a solution containing silver together with something which 
has the power to separate the silver in the metallic state 
when heated. Under these circumstances the silver is 
deposited in a smooth, lustrous layer. Mirrors are made 
in this way. 



THE COPPER FAMILY, 207 

Silver Nitrate, AgXOg, is also called ^^ lunar caustic/^ 
as it has the power to destroy the flesh, and is therefore 
used to burn out wounds. It is prepared by dissolving 
silver in dilute nitric acid. Marks made by silver nitrate 
turn black in the sunlight. Hence this salt is used as a 
constituent of indelille inks. When working with silver 
salts the fingers are apt to become stained. ^ These stains 
and generally any spots made by silver salts can be removed 
by a solution of potassium cyanide, which forms soluble 
i?alts with compounds of silver.* 

Experiment 117.— Dissolve a ten or twenty-five cent piece in 
dilute nitric acid. What action takes place? Dilute the sola- 
tion to 200 to 300 c.c. with water. What is the color of the solu- 
tion ? What does this indicate ? Does this color prove that 
copper is present ? Add a solution of common salt until it ceases 
to produce a precipitate. The chemical change that takes place 
is expressed by the equation 

AgNOs 4- l^aCl = AgCl + NaNOa. 

Insoluble. 

The copper nitrate is not changed and remains in solution. 
Filter off the white silver chloride and carefully wash with hot 
water. Dry the precipitate on the filter, by placing the funnel 
with the filter and precipitate in an air-bath heated to about 110°. 
Remove the precipitate from the filter and put it into a porcelain 
crucible. Heat gently with a small flame until the chloride is 
melted. Cut out a piece of sheet-zinc large enough to cover the 
silver chloride. Lay it on the silver chloride. Now add a little 
water and a few drops of dilute sulphuric acid, and let the whole 
stand for twenty-four hours. The silver chloride is changed to 
silver, and zinc chloride is formed : 

Zn + 2AgCl = ZnCh + 2Ag. 

* Some years ago a scoundrel disfigured the beautiful marble 
statue of the great chemist Llebig which is in Munich by bespatter- 
ing it with a solution of nitrate of silver. The professors of chem- 
istry in the university succeeded, however, in removing the stains 
completely by applying a paste containing potassium cyanide. 



2o8 THE ELEMENTS OF CHEMISTRY, 

Take out the piece of zinc and wash the silver with a little 
dilute sulphuric acid, and then with water. Dissolve the silver 
in dilute nitric acid and evaporate to dryness on the water-bath, 
so that the excess of nitric acid is driven off. Dissolve the resi- 
due in water, and put the solution either in a bottle of dark glass 
or one wrapped in dark paper. 

Experiment 118. — To a few cubic centimetres of water in a 
test-tube add 5 to 10 drops of the solution of silver nitrate just 
prepared. To this dilute solution add a little of a dilute solution 
of sodium chloride. What takes place ? Place it aside where the 
light can shine upon it, and notice the change of color which 
gradually takes place. In the same way make the bromide by 
adding potassium bromide, and the iodide by adding potassium 
iodide to silver nitrate. 

Photography. — The last experiments showed that the 
chloride, bromide, and iodide of silver are insoluble in 
water and are changed by light. The art of jjliotography 
is based upon the changes Avhich certain compounds, 
especially salts of silver, undergo when exposed to the 
light. A plate of glass, or celluloid film, is covered with 
a thin layer of an emulsion of the halogen salts of silver* 
in gelatin, albumin, or collodion. The plate or the film 
is then exposed in the camera to the action of the light 
from the object to be photographed. Where the light 
acts upon the salt it is changed, while where the light 
does not act it is not changed. An image of the object 
towards which the plate was directed is thus left on the 
plate. The image must be developed by treating the plate 
with a solution of pyrogallic acid, ferrous oxalate, or some 
other reducing agent. After the image is developed, the 
plate is treated with something which dissolves the 
unchanged silver salt in order to '' fix ^' it. The best sub- 
stance for this purpose is a solution of sodium hyposulphite 
(called hypo). 



CHAPTEK XXIL 

THE ALUMINIUM FAMILY— THE IROK FAMILY: IRON, 
COBALT, NICKEL. 

Aluminium, Al {At. Wf. 27). — Alaminiam is the only 
element of the family which it represents that need be 
taken up here. It is an extremely important element that 
occurs yery widely distributed in nature. Among the 
many im.portant and widely-distributed minerals that con- 
tain aluminium are feldspar, mica, and cryolite. The 
rock granite contains both feldspar and mica. Clay is 
essentially a silicate of aluminium. 

Preparation of Aluminium. — Aluminium is prepared by 
passing an electric current through a bath of molten 
cryolite containing aluminium oxide in the form of corun- 
dum in solution. Iron pots are used. These form one 
electrode, while carbon rods are used for the other elec- 
trode. 

Properties. — Aluminium has a strong lustre; its color is 
like that 'of tin. It is very strong and yet malleable. It 
is lighter than most metals in common use, its specific 
gravity being 2.5 to 2.7, while that of iron is 7.8, that of 
silver 10.57, and that of tin 7.3. Further, it does not 
change in dry or moist air. These properties give it great 

209 



2ro THE ELEMENTS OF CHEMISTRY. 

value, and it is coming into more and more extensive use. 
It is used in the preparation of ornaments^ and of useful 
articles in which lightness is of importance, as in tele- 
scopes and opera-glasses. An alloy with a small percentage 
of silver is used for the beams of chemical balances. 
Aluminium bronze, an alloy with copper, is also used quite 
extensively. High temperatures (about 3000° C.) are 
attained by burning cartridges containing aluminium and 
ferric oxide. Practical use is made of this process in 
welding. 

Aluminium Oxide, AI2O3. — This compound occurs in 
nature in the form of ruby, sapphire, and corundum. It 
is very hard, and as emery, which is powdered corundum, 
is used for polishing. It is made artificially by heating 
the hydroxide, A1(0H)3: 

2A1(0H)3 = Al,03 + 3H,0. 

Alums. — Aluminium sulphate forms complex com- 
pounds with the sulphates of the alkali metals, all of 
which crystallize beautifully. Potassium alum is the best 
known of these. It may be regarded as derived from 
2 molecules of sulphuric acid, 2H2SO^ = H^S20g, by the 
substitution of 1 atom of aluminium for 3 atoms of 
hydrogen, and of 1 atom of potassium for the fourth atom 
of hydrogen; thus, AlKS^Og or A1K(S0J2. The crystals 
always contain 12 molecules of water, the complete formula 
being A1K(S0J2 + 121120. Similarly, sodium alum is 
Ama(S0j2 + I2H2O, and ammonium alum, A1NH,(S0,)2 
+ I2H2O. 

Uses of Alum. — Alum and other compounds are used in 
dyeing cotton cloth. Colors do not adhere to cotton fibre 



THE ALUMINIUM FAMILY, 211 

as they do to wool and silk. On adding aluminium 
hydroxide or alum to the cotton the dye-stuffs unite with 
these and form insoluble compounds. Substances that 
have the power of combining with dye-stuffs in this way 
are called mordants. Alum is an acid salt and has the 
power of decomposing carbonates. It is therefore some- 
times wrongly used as a constituent of ^^ baking powders ^^ 
in connection with sodium bicarbonate. 

Aluminium Silicates. — The silicate of aluminium occurs 
in nature in enormous quantities, in combination with 
other silicates forming some of the most important minerals. 
The most abundant of these is ordinary feldspar, AlKSigOg- 
When these silicates are subjected to the influence of the 
air, rain, frost, etc., they suffer decomposition. The sili- 
cate of the alkali metal dissolves and is washed away, while 
aluminium silicate is partly left behind and is also partly 
washed away. Pure aluminium silicate is known as 
kaolin, and has the composition Al^(SiOj3 + 4H2O. The 
impure varieties are called clay. 

Porcelain, etc. — Kaolin is used for making porcelain. 
For this purpose it is mixed w^ith water and. moulded into 
the proper shape and then heated to a high temperature 
in a furnace. The ordinary varieties of clay are used for 
making common earthenware vessels and bricks. Earthen- 
ware and porcelain are glazed in two ways: Porcelain, 
by coating it with an easily-fusible substance and heating 
to a high temperature; earthenware, by heating to a 
strong red heat in a furnace and throwing in a quantity 
of damp salt. The salt is decomposed and sodium silicate 
is formed. This fuses on the surface of the vessels and 
forms a layer which is not porous. 



212 THE ELEMENTS OF CHEMISTRY. 

Ultramarine. — The substance known as ultramarine or 
lapis lazuli consists of a silicate of aluminium and sodium^, 
together with a sulphide of sodium. The coloring-matter 
obtained by powdering it was formerly expensive, but it is 
now made artificially by the ton, and the color of the 
artificially-prepared substance is even more beautiful than 
that of the natural. It is made by heating a mixture of 
clay, dry sodium carbonate, sulphur, and wood-ashes 
without access of air. 

Iron, Fe {At, Wt. 56). — At the present time it is un- 
doubtedly true that iron is the most important metal for 
man. It occurs in the form of magnetite. FCgO^, and 
liematite, Y^^0^\ as the carlonate, or siderite, FeCOg; in 
combination with sulphur as iron pyrites^ FeS2; and as 
silicates and liydrated oxides^ or hydroxides. Iron in the 
metallic state is found in the form of meteors or masses 
which fall upon the earth from the outer space. 

Extraction of Iron from its Ores. — The extraction of iron 
from its ores is theoretically simple, the essential steps 
being these : 

(1) The conversion of the ore into the oxides, unless 
the oxides themselves are used. 

This is accomplished by roasting them. If sulphides 
are roasted the sulphur passes off as sulphur dioxide, and 
the iron remains as the oxide. Further, water is driven 
off, and the carbonate is decomposed into the oxide and 
carbon dioxide. 

(2) Eeduction of the oxides by means of charcoal or 
coke. 

This is accomplished by mixing the ore with the reduc- 
ing agent and heating in a blast-furnace. The blast- 



THE IRON FAMILY, 



213 



furnace is constructed of fire-brick and masonry. It is 
from 25 to 80 or 90 feet high, and 
from 15 to 18 feet wide in the 
widest part. An idea of the con- 
struction is given by Fig. 39. 
Alternate layers of ore and fuel are^ 
introduced into the top of the fur- 
nace. A /i^x is also added. This' 
is usually limestone or quicklime. 
The object of the flux is to form a 
fusible substance with the earthy 
constituents of the ore. As the 
iron is reduced it melts, and the 
compound formed with the flux also 
melts. The molten iron being the ' 
heavier liquid sinks to the bottom 
followed by the other, which is 
called the slag. The iron collects 
in the bottom of the furnace, called 
the crucible, and is drawn off in the liquid condition. 

The reduction is largely accomplished by carbon mon- 
oxide. In the lower part of the furnace the fuel burns to 
carbon dioxide, but in its upward passage this comes in 
contact with hot carbon, and is then reduced to the mon- 
oxide. The hot monoxide in contact with the oxides of 
iron reduces these, and is itself converted into the dioxide. 

Pig-iron. — The iron drawn off from the furnace is called 
jng-iron. It is always impure, containing phosphorus, 
sulphur, silicon, and as much as 2 to 6 per cent of carbon. 
It is brittle and easily fusible^ and is used for casting, 
being known as cast-iron. 




214 



THE ELEMENTS OF CHEMISTRY. 



Wrought-iron. — When the carbon, silicon, and phos- 
phorus are removed from pig -iron it becomes tough and 
malleable. It is now lurought-iron. Cast-iron is converted 
into wrought-iron in one of two ways: 

(1) Puddling, — The puddling-furnace has a flat, oval 
hearth and a low, arched roof. The sides of the hearth 
are lined with iron ore (oxide). Coal is burned on a grate, 
and the flame passes into the furnace at one end and out 
at the other, thus coming in contact with the roof and being 
reflected downward upon the charge of iron. The cast-iron 
is melted, and the carbon and silicon are removed from it, 
partly by the oxygen of the air, but principally by that in 
the iron ore, which is itself thus reduced to wrought-iron. 

(2) Bessemer Process, — Molten cast-iron is poured into 
a large vessel called a converter, Fig. 40. 
The carbon and silicon are oxidized, and 
removed by a blast of air forced through 
the metal from below. No fuel is used, 
as the heat generated by the oxidation 
of the carbon and silicon is sufficient to 
raise the temperature above 2100° C. 
By adding molten cast-iron to the 
product, steel containing any desired per- 
centage of carbon is obtained. 

Fig. 40. The Bessemer process is now employed 

on an enormous scale. The product is used in making 
cannon, rails, axles, etc. 

Bessemer steel often contains less than 0. 6 per cent of 
carbon. 

Pure Iron. — Pure iron is almost unknown. It is a white 
metal with a strong lustre. In moist air it rusts; that is, 




THE IRON FAMILY, 215 

it becomes covered with a layer of oxide and hydroxide 
which is formed by the action of the air and water. The 
wire used for pianos is nearly pure; but if this is dissolved 
in hydrochloric or sulphuric acid, small black particles of 
carbon will remain undissolved. The odor noticed when 
ordinary iron is dissolved in acid is due to the presence of 
impurities. 

Compounds of Iron. — Iron, like mercury and copper, 
forms two series of compounds which differ markedlj^ from 
each other. These are the ferrous a^nd ferric compounds. 
Thus with chlorine it forms two chlorides, one of which, 
ferrous chloride, has the composition expressed by the 
formula FeCl^; the other, ferric chloride, by FeClg. It 
appears from a study of the relative weights of these 
chlorides in the state of vapor (see Chapter XIV., page 
138) that the above formulas should be doubled, so that 
ferrous chloride is now commonly represented by Fe.Cl^, 
and ferric chloride by Fe2Clg. For our purpose the 
simpler formulas will answer just as well. Similarly there 
are two oxides, FeO and Fe203; two sulphates, ferrous 
sulphate, FeSO^, smd ferric sulphate, Fe2(SOj3, etc. 

Change of Ferrous to Ferric Compounds. — Ferrous com- 
pounds are slowly changed to ferric compounds by contact 
with the air, and readily by oxidizing agents, such as nitric 
acid, potassium chlorate, etc. When, for example, ferrous 
hydroxide, Fe(0H)2, is exposed to the air suspended in 
water, it slowly changes to ferric hydroxide, Fe(0H)3. 
The change is represented by the equation 

2Fe(OH)2 + H2O + = 2Fe(OH)3. 

So, also, when ferrous chloride is left standing in solu- 



2i6 THE ELEMENTS OF CHEMISTRY, 

tion in hydrochloric acid it changes to ferric chloride, and 
the change is rapidly effected by boiling with a little nitric 
acid which gives u^ oxygen : 

2FeCl, + 2HC1 + = 2FeCl3 + H,0. 

Ferrous Chloride, FeCl2 , is formed by dissolving iron in 
hydrochloric acid. 

Experiment 119. — Dissolve a little iron wire in dilute hydro- 
chloric acid. Hydrogen is evolved, accompanied by small quan- 
tities of other gases the formation of which is due to the presence 
of impurities in the iron, and carbon is left undissolved as a 
black residue. To a few drops of the solution in water in a test- 
tube add at once caustic soda. This precipitates ferrous hydrox- 
ide, re(0H)2, which changes color rapidly, becoming finally red- 
dish-brown. Pure ferrous hydroxide is white. As it passes to 
the ferric condition it becomes dirty green, and darker and darker 
until it is reddish-brown, which is the color of ferric hydroxide, 
Fe(0H)3. Heat another small portion of the solution of ferrous 
chloride to boiling, add two or three drops of concentrated nitric 
acid and boil again. Kepeat this operation two or three times. 
The ferrous chloride is thus oxidized to ferric chloride. It will 
be noticed that the color of the solution after the oxidation is red- 
dish-yellow, whereas before the oxidation it was nearly colorless 
or slightly greenish. Add caustic soda to the solution of ferric 
chloride. A reddish-brown precipitate of ferric hydroxide will 
be formed. Just as in this case you have passed from ferrous 
chloride to ferric chloride by oxidation, so you cau pass back 
again to the ferrous compound. Thus by adding a little zinc to 
a solution of ferric chloride in which hydrochloric acid is present, 
the hydrogen evolved extracts chlorine from the ferric chloride 
and converts it into ferrous chloride : 

FeCls + H == FeCU + HCl. 

Ferrous Sulphate, FeSO, + TH^O.— This salt, which is 
commonly known as ^^ green vitriol" or ^^ copperas/^ is 
formed by the action of sulphuric acid on iron. [What is 
" white vitriol ^^ ? " blue vitriol '' ?] It is extensively 
used in the preparation of ink and in dyeing. 



THE IRON FAMILY. 217 

Inks. — Iron iuks are made by treating solutions of 
tannic acid, which is obtained from nut-galls, with ferrous 
sulphate or copperas. There are many kinds of ink in use 
which are not made in this way. Printers^ ink contains 
lamp-black. So also does India ink. Inferior inks are 
made of aniline dyes, which are made from substances 
obtained from coal-tar. 

Iron Alum, FeK(S0j2 + I2II2O, is formed by bringing 
ferric sulphate and potassium sulphate together. It 
resembles ordinary alum, A1K(S0J2 + I2II2O, but differs 
from it in containing iron instead of aluminium. 

Ferric Oxide, Fe^Og, occurs in nature in lustrous 
crystals, as hematite^ and as a red mass. It is prepared 
on the large scale by heating copperas in the air, when the 
change represented in the following equation takes place: 

2FeS0, = ^Qfi, + SO3 + SO2. 

The oxide thus obtained is a dark-red powder called rouge. 
It is used for polishing glass and as a paint. 

Ferroso-ferric Oxide, FCgO^, or magnetic oxide of iron, 
is found in nature in the form of loadstone; It is formed 
when iron is burned in oxygen (see Experiment 26). 

The sulphides of iron have been repeatedly mentioned. 

Ferrous Sulphide, PeS, is made by heating sulphur and 
iron together in proper proportions. It is used in making 
hydrogen sulphide. [Explain how.] 

Iron Pyrites, EeS2, is a yellow crystallized substance 
very abundantly found in nature. When heated in a 
closed tube sulphur is given off. When heated in an open 
vessel as upon a shallow iron pan or spoon, the sulphur is 
oxidized to sulphur dioxide, and the iron is left in the 



2i8 THE ELEMENTS OF CHEMISTRY, 

form of the oxide. [Verify these statements by experi- 
ment.] 

Nickel, Ni {At, 117. 58.3), is found in meteoric iron and 
in combination with arsenic. It forms two series of salts 
corresponding to the two hydroxides, nickelous hydroxide, 
Ni(0H)2, and nickelic hydroxide, Ni(0H)3. Mckel is 
used for making coins, and for plating other metals. It 
is not acted upon by the air. 

Cobalt, Co {At, Wt. 58.6), is found in combination with 
arsenic and suljDhur, and also in small quantities accom- 
panying nickel in meteoric iron. 

Cobalt compounds are used on account of their colors. 
Smalt is made by fusing glass with a cobalt compound, 
when a blue mass is obtained which is powdered and used 
as a paint. When cobaltic oxide and aluminium oxide are 
fused together a dark-blue substance is formed which is 
known as cohalt ultramarine. 



CHAPTER XXIII. 
MANGANESE— CHROMIUM— URANIUM— BISMUTH. 

Manganese, Mn {At. Wt. 54.6). — Manganese is found in 
nature in the form of the oxides, of which manganese 
dioxide, or the black oxide of manganese, occurs most 
abundantly. With oxygen it forms the following com- 
pounds: manganous oxide, MhO; manganic oxide, Mn^Og; 
manganoso-manganic oxide, MUgO^; manganese dioxide, 
Mn02; ^ndi permanganic anhydride, Mn^O^. 

Manganese resembles aluminium and iron in some 
respects. Like iron it forms two series of salts, the 
manganous and manganic series, which differ from each 
other very much as ferrous and ferric compounds do. 

Chromium, Or {At. Wt, 51.7). — This element is com- 
paratively rare, and occurs almost entirely in combination 
with oxygen and iron as chromic iron, FeCr^O^ or Fe(Cr02)2- 

Potassium Chromate, K^CrO^, is formed when finely- 
powdered chromic iron is heated with potassium carbonate 
and potassium nitrate. 

Potassium Bichromate, K^Cr^O,. — This is the form in 
which chromium is most frequently met with. It is 
formed from the chromate by adding acetic or nitric acid. 
The change is represented thus : 

2K2CrO, + 2HNO3 = 2KNO3 + K^Cr^O, + H^O. 

219 



2 20 THE ELEMENTS OF CHEMISTRY. 

The relation between the chromate and the bichromate 
will be more readily understood by considering the acids 
from which they are derived. These are chromic acid, 
H2CrO^ , and bichromic acid, ^Jurfi^. The latter may be 
regarded as derived from the former by loss of water: 

2H,CrO, ^ H,Cr,0, + H^O. 

Experiment 120. — Potassium bichromate is converted into the 
chromate by adding a solution of potassium hydroxide until the 
color becomes pure yellow : 

K^Cr^OT + 2K0H = 2Y.^QrO, + H2O. 

Convert 10 to 20 grams potassium bichromate into the chro- 
mate. Evaporate to crystallization. Compare the salt thus 
obtained with potassium bichromate. 

Experiment 121. — Convert the potassium chromate just ob- 
tained into potassium bichromate by adding dilute nitric acid 
until the color is red. Evaporate to crystallization. 

Both the chromate and bichromate are good oxidizing 
agents. 

Experiment 122.— Treat a little of each salt in a test-tube with 
hydrochloric acid. [What evidence do you get that the salts are 
good oxidizing agents ?] 

Chrome-yellow. — The chromates of lead and barium are 
insoluble in water. They are yellow. The lead salt is the 
well-known paint clirome-yelloiv. 

Experiment 123.— Add a little of a solution of potassium chro- 
mate or bichromate to a solution of barium chloride, and of lead 
acetate or nitratie. 

Chrome Alum is a salt related to ordinary alum, but 
containing chromium instead of aluminium. Its formula 
is CrK(S0j2 + l^H^O. The alums have analogous 
formulas : 



MANGANESE- CHROMIUM- URANIUM-^BISMUTH, 2 2 1 

Ordinary alum A1K(S04)2 + 12HaO. 

Iron alum FeK(S04). + I2H2O. 

Chrome alum CrK(S04)2 + I2H2O. 

XTranium, U {At. Wt. 237.7). — This element occurs 
mostly in the form of the oxide TJfi^ known as pitchblende. 

Bismuth, Bi {At. Wt. 206.9), occurs mostly native, and 
is obtained by heating the ores and allowing the molten 
bismuth to run out. In appearance it closely resembles 
antimony. 

Bismuth forms alloys which melt at low temperatures. 
The best known of these is '^fusible metal/^ which is 
composed of lead, tin, and bismuth. TVood^s metal melts 
at 60°. 5, while its lowest melting constituent, tin, melts 
at 233®. It consists of bismuth, lead, cadmium, and tin. 

The chief compound of bismuth and oxygen is the 
yellow oxide Bi203, which is formed when bismuth is 
burned in the air. 

The principal salt of bismuth is the nitrate Bi(N03)3 + 
SHgO. Another nitrate of bismuth is used in medicine. 



CHAPTER XXIV. 
LEAD— TIN— PLATINUM— GOLD. 

Lead, Pb {At. Wt. 205.35). — Lead occurs in combina- 
tion in several forms in nature, as, for example, in the 
sulphate, carbonate, chromate, and sulphide. The sul- 
phide, PbS, known as galena^ or galenite, is the most 
important ore of lead. 

Extraction of Lead from its Ore. — The extraction of lead 
from its ore is accomplished in one of two ways : 

(1) By heating the sulphide with iron, when the latter 
combines with the sulphur, forming iron sulphide, while 
the lead is set free. 

(2) By roasting the sulphide until it is partly converted 
into lead oxide and lead sulphate; then heating the mix- 
ture without access of air, when the two reactions take 
place which are represented in these equations: 

PbS + 2PbO = 3Pb + SO,; 
PbS + PbSO, = 2Pb + 2S0,. 

The lead is thus set free, and the sulphur driven off as 
sulphur dioxide. 

Properties of Lead. — Lead is a bluish-gray metal with a 
high lustre which tarnishes rapidly when exposed to 
the air. It is soft and not very strong. It melts at 
about 325°. All lead salts are poisonous. Nitric acid 

222 



LEAD— TIN-PLATINUM— GOLD, 223 

dissolves it, but li3^drochloric and dilute sulphuric acids 
do not. It is precipitated in metallic form from a solu- 
tion of one of its salts by metallic zinc. The formation is 
sometimes called the ^^ lead-tree ^^ or "'Arbor Saturni/^ 

Experiment 1 24. — Dissolve 6 or 8 grams lead acetate (sugar of 
lead) in a litre of water, add a few drops of acetic acid, and put 
the solution in a wide-mouthed bottle. Suspend a piece of sheet- 
zinc in the middle of the solution, and let it stand. The lead will 
be deposited slowly in crystallized form. At the same time the 
zinc will pass into solution. The zinc takes the place of the lead: 

Zn + Pb(N03)2 = Zn(N03)2 + Pb. 

Lead Water-pipes. — Pipes for conveying water are fre 
quently made of lead, and under most circumstances there 
is no danger in this; but some waters, particularly such 
as are rich in carbon dioxide, act upon lead and dissolve 
it in small quantity. Such waters are exceedingly dan- 
gerous. If air and water together act upon lead, it is 
much more readily acted upon than when air is excluded. 
In moist air lead tarnishes. 

Oxides of Lead. — Lead forms three compounds with 
oxygen, viz.: lead suboxide, ^\0; lead oxide, PbO; and 
lead peroxide, Pb02. Bed lead, or minium, is a mixture 
or a compound of the oxide and peroxide, and has approxi- 
mately the composition Pb^O^. 

Lead Oxide, PbO, is commonly known by the name 
litharge. It is formed by the oxidation of molten lead in 
contact with the air. 

Minium, Red Lead, Pb30,(= 2PbO + PbO^).— When 
litharge is heated in the air to 400° it takes up oxygen and 
is converted into 7ninium^ or red lead. When minium is 
heated to a high temperature it gives up oxygen and is 
again converted into yellow lead oxide. Treated with 



2 24 THE ELEMENTS OF CHEMISTRY, 

nitric acid, a part is dissolved, forming lead nitrate, while 
lead peroxide, a brown powder, remains behind. 

Experiment 125. — Treat a little minium with ordinary dilute 
nitric acid, and note the change in color. Does lead pass into 
solution ? How do you know ? 

Lead Peroxide, PbOg, conducts itself somewhat like 
manganese dioxide. When treated with hydrochloric acid 
chlorine is evolved : 

PbO, + 4HC1 = PbCl, + 2H,0 + 2C1. 

Experiment 126. — Treat a little lead peroxide with hydrochloric 
acid in a test-tube. In what form is the lead after the experi- 
ment ? Is the product soluble or insoluble in water ? 

The sidjoliate, chromate, and chloride are formed by add- 
ing a soluble sulphate, chromate, and chloride to a solution 
of a lead salt. The chromate is the well-known chrome- 
yelloiv. 

Lead Carbonate, PbCOg, is the well-known and much- 
used pigment ivhite lead. The objection to its use in a 
laboratory is that it turns black in the presence of even 
small quantities of hydrogen sulphide. Zinc-white does 
not act in this way, as zinc sulphide is a white substance. 

Tin, Sn {At. Wt. 117.6).— Tin occurs in nature mostly 
as tin-stone, which is the oxide SnOg. The metal is 
obtained from the ore by reducing with charcoal. It is a 
white metal that resembles silver in appearance. It is soft 
and malleable, and can be hammered out into very thin 
sheets, forming the well-known tin-foil. At 200° it is 
brittle; and at 233° it melts. It does not change in the 
air at ordinary temperatures. Ordinary concentrated 
nitric acid oxidizes it, the product being a compound of 



LEAD— TIN—PLA TINUM- GOLD. 225 

tin, oxygen, and hydrogen, known as metastannic acid, 
which is a white powder insohible in nitric acid and in 
water. 

Extraction of Tin from its Ore. — The oxide or tinstone 
is pulverized, mixed with charcoal, and heated in a fur- 
nace, when the tin appears in the molten condition. 

Uses of Tin. — Owing to the fact that tin does not change 
in the air it is used as a covering for other metals. 
Ordinary tin-icare is made of sheets of iron covered with 
tin. An inferior variety of tin-ware is manufactured 
containing lead. If such ware is used for cooking-utensils 
or for making cans for preserving fruit and vegetables 
serious results may follow, as the acids of the food may 
dissolve enough lead to form poisonous liquids. Copper 
covered with tin is also used for various purposes, as for 
bath-tubs and pins. 

Alloys of Tin. — Among the valuable alloys containing 
tin are solder, which consists of tin and lead; Iritannia 
which consists of 9 parts of tin and 1 part of antimony; 
bronze and bell-metal, which consist of tin and copper. 

Soldering. — Soldering in general is any process by which 
metals are made to adhere by means of other metals added 
in the molten condition. Ordinary soldering consists in 
joining metals together by means of a solder consisting of 
about equal parts of lead and tin. In order that the solder 
may hold, it is necessary that the surfaces of the metal to 
which it is applied should be bright. This is brought 
about by the use of rosin or by washing with a little acid 
and then adding some borax, which in the molten condi- 
tion dissolves any metallic oxides which may be present, 
leaving the surfaces bright. There is some danger in the 



226 THE ELEMENTS OF CHEMISTRY, 

use of solder for tin cans, as it is possible for the contents 
to get in contact with the solder unless the work is done 
with unusual care. 

Stannous and Stannic Compounds. — Tin forms two 
classes of compounds, the stannous and stannic com- 
pounds. These do not bear to each other the same rela- 
tion as that which exists between cuprous and cupric 
compounds, or that between ferrous and ferric compounds. 
In stannous compounds the tin appears to be bivalent, as 
indicated by the formulas SnCl2, SnO, SnS, which 
respectively represent stannous chloride, oxide, and sul- 
phide. In stannic compounds, on the other hand, the tin 
appears to be quadrivalent, as indicated by the formulas 
SnCl^, Sn02, SnSg, which respectively represent stannic 
chloride, oxide, and sulphide. 

Stannous Chloride, SnCl2, and Stannic Chloride, SnCl^, 
are the most used compounds of tin. They find applica- 
tion in dyeing. The former is known as tin-salt. It is 
made by dissolving tin in hydrochloric acid. 

Stannic Sulphide, SnS^ , is a yellow substance used under 
the name mosaic gold as a pigment in decorating. 

Platinum, Pt [At, Wt. 193.3), occurs almost alwaj^s 
accompanied by the rare metals iridium, palladium, and 
osmium, in the form of alloys. The ore is found in the 
Ural Mountains, in California, Australia, and a few other 
places. It is prepared by treating the ore with strong 
aqua regia, which dissolves the platinum, together with 
some iridium. The chlorplatinic acid thus formed is 
precipitated by means of ammonium chloride, with which, 
as with potassium chloride, it forms a difficultly soluble 
compound, (NIIj2PtClg. When this is heated to a suffi- 



LEAD— TIN— PL A TINUM—GOLD, 227 

ciently high temperature it is decomposed, leaving metallic 
platinum behind. 

Properties of Platinum. — Platinum is a grayish-white 
metal with a high lustre. Its specific gravity is 21.15, it 
being one of the heaviest substances known. The specific 
gravity of iron is 7.8, that of lead 11.4. In other words, 
a piece of platinum weighs nearly three times as much as 
a piece of iron of the same dimensions, and nearly twice 
as much as a piece of lead of the same bulk. Platinum is 
not dissolved by hydrochloric, nitric, or sulphuric acid; 
but aqua regia dissolves it, forming chlorplatinic acid, 
HgPtClg. Fusing caustic alkalies attack it; sodium car- 
bonate does not. It does not change in the air, and does 
not melt except in the flame of the oxyhydrogen blow-pipe 
or in the electric furnace. It resists the action of most 
substances. 

TJses of Platinum. — The properties of platinum make it 
extremely valuable to the chemist. Platinum crucibles 
and evaporating-dishes, foil, and wire are in constant use 
in every chemical laboratory, and it is difficult to see how 
we could get along without them. Large retorts of 
platinum are used for the purpose of concentrating sul- 
phuric acid and distilling it. 

Gold, Au [At, Wt. 195.7). — Gold usually occurs native. 
It is found enclosed in quartz, or more frequently in quartz 
sand. It is separated mechanically by washing, and then 
extracted with mercury, which forms an amalgam with it. 
The amalgam is afterwards heated, when the mercury 
passes over and the gold remains behind. Gold is also 
extracted from its ores by means of chlorine or potassium 
cyanide. 



2 28 THE ELEMENTS OF CHEMISTRY. 

Properties of Gold. — Gold is a yellow metal with a high 
lustre. It is quite soft and extremely malleable. It can 
be beaten into leaves not more than y-o^o-o of a millimetre 
thick. Its speciJBc gravity is 19.3. It combines directly 
with chlorine^ but not with oxygen. Hydrochloric, nitric, 
and sulphuric acids do not act upon it; but aqua regia. 
dissolves it, forming chlorauric acid, HAuCl^. On account 
of the fact that gold resists the action of other substances 
it was formerly spoken of as the hing of metals, and there- 
fore the mixture of hydrochloric and nitric acids which 
dissolves it was called aqua regia, or royal water. 

Uses of Gold. — Gold ware and coin are made of an alloy 
of gold and copper. The standard gold coin of the United 
States contains nine parts of gold to one of copper. The 
composition of gold for jewelry is usually stated in carats. 
Pure gold is 24-carat gold; 20-carat gold contains 20 
parts gold and 4 parts copper; 18-carat gold contains 18 
parts gold and 6 parts copper, etc. 



CHAPTEE XXV. 
SOME FAMILIAR COMPOUNDS OF CARBON. 

Organic Chemistry. — When the compounds that are 
obtained from plants and animals were first studied it was 
supposed that they are entirely different in every way from 
the compounds obtained from earthy or mineral sub- 
stances. The former were called organic substances, for 
the reason that they were obtained from organized beings; 
while the latter were called inorganic substances. Organic 
substances were the subject of Organic Chemistry, and 
inorganic substances formed the subject of Inorganic 
Chemistry. These names are still in use, though they 
have -lost their original meaning. Organic Chemistry 
means now only the Chemistry of the Componncls of 
Carbon, 

Occurrence of the Compounds of Carbon. — The most 
widely distributed compound of carbon is carbon dioxide, 
which, as you have learned, is the starting-point of all life 
on the globe. All liying things are formed from it either 
directly or indirectly. The substances that occur in 
largest quantity in plants are cellulose and starch; but 
besides these a large number of other substances are 
found, as the sugars, the alkaloids, — of which, morphine, 
quinine, and nicotine, are examples, — oxalic acid, malic 
acid, tartaric acid, citric acid. In animals, too, occur 
many substances, as the fats, albumin, fibrin, etc. 

229 



230 THE ELEMENTS OF CHEMISTRY, 

Certain natural processes that are not thoroughly un- 
derstood have given rise to the formation of a complex 
mixture of organic compounds, principally hydrocarbons, 
in petroleum (page 116). 

Distillation of Coal. — The destructive distillation of coal 
for the purpose of making illuminating-gas, and the 
formation of coal-tar^ have already been referred to. 
Coal-tar is one of the most important sources of com- 
pounds of carbon. The hydrocarbons benzene, C^Hg, 
toluene, C^Hg, xylene, CgH^^, naphthalene, C^^Hg, anthra- 
cene, C^^HjQ, etc., are obtained from this source. 

Distillation of Wood. — Wood is heated in closed vessels 
mostly for the purpose of making charcoal, as already 
explained. Among the products obtained from this source 
are wood-alcohol, or methyl alcohol^ and pyroligneous acid, 
or acetic acid. Large quantities of acetic acid are prepared 
in this way. 

Distillation of Bones. — In order to make bone-black, 
bones are subjected to destructive distillation. The oil 
that passes over, called hone- oil, is collected. 

Fermentation. — A number of the most important com- 
pounds of carbon are formed by a process known as 
fermentation. This is a general term meaning any process 
in which a chemical change is effected by means of minute 
animal or vegetable organisms. The best known example 
of fermentation is that of sugar, which gives rise to the 
formation of ordinary alcohol. The organism that causes 
the change is called 2, ferment. 

Classes of Compounds of Carbon. — The chief classes of 
these compounds are the hydrocarbons,, some of which have 
already been treated of (see page 116); the alcohols; the 



SOME FAMILIAR COMPOUNDS OF CARBON. 



231 



acids; the ethers; and the efJiereal salts. First a few of 
the best known examples of each of these classes will be 
taken up, and afterwards some other familiar compounds 
which do not belong to any one of these classes. 



Alcohols. 

Methyl Alcohol, Wood-spirit, Wood Alcohol, CHp.— 

This is formed by the distillation of wood, and is separated 
from the other products thafc are formed at the same time. 
It has, when pure, a pleasant odor and taste and acts upon 
the animal system much as ordinary alcohol does. It 
burns without giving light or smoke, and may therefore 
be used in lamps for heating purposes as ordinary alcohol 
is. It is used in the manufacture of varnishes. 

Ethyl Alcohol, Spirits of Wine, C^H^O.— This well- 
known substance is formed by the fermentation of grape- 
sugar or glucose. 

Experiment 127. — Dissolve 150 grams commercial grape- 
sugar, or 150 c.c. table syrup, in 1 to 2 litres of water in a flask, 




Fig. 41. 



Connect the flask by means of a bent glass tube with a cylinder 
or bottle containing clear lime-water. The vessel containing the 
lime-water must be provided with a cork with two holes. Through 



232 THE ELEMENTS OF CHEMISTRY, 

one of these passes the tube from the fermentation-flask; through 
the other a tube connecting with a vessel containing solid 
caustic potash, the object of which is to prevent the carbon dioxide 
in the air from acting upon the lime-water. The arrangement 
of the apparatus is shown in Fig. 41. Now add to the solution 
of grape-sugar or syrup a little fresh brewer's yeast ; close the 
connections and allow to stand. Soon an evolution of gas will 
begin, and, as this passes through the lime-water, a precipitate 
will be formed which can be shown to be calcium carbonate. 

What Change takes place in the Sugar ? — If the solution 
in the flask is examined carefully it will be found to con- 
tain alcohol and no sugar. Grape-sugar has the composi- 
tion expressed by the formula CgH^206. By fermentation 
it is decomposed, forming alcohol, C^fi, and carbon 
dioxide, CO2. The decomposition is expressed by the 
equation 

C,H,0, = 3C,H,0 + 2C0,. 

What Causes the Change ? — It has been found that the 
change of grape-sugar is caused by small organized bodies 
that grow in the solution. These bodies are contained in 
ordinary yeast. 

Germs in the Air. — When fruit-juices that contain sugar 
are exposed to the air they undergo fermentation without 
the addition of yeast. This is due to the fact that the 
germs or seeds of the bodies that cause fermentation are 
everywhere floating in the air. Hence, when a liquid in 
which these seeds can grow is exposed to the air, the bodies 
are formed, and fermentation takes place. 

Different Kinds of Fermentation. — The fermentation 
that yields alcohol is only one of manykinds. Among the 
others are: (1) lactic-acid fermentation, which takes place 



SOME FAMILIAR COMPOUNDS OF CARBON, 233 

in the souring of milk; and (2) acetic-acid fermentation, 
which causes the transformation of alcohol into acetic acid. 
The latter ferment is contained in ^^ mother of vinegar." 

Distillation of Fermented Liquids. — In order to get the 
alcohol from liquids that have undergone fermentation 
they must be distilled. For this purpose very efficient 
forms of stills have been devised, so that the alcohol 
passes over nearly free from other substances. Usually it 
contains impurities known a,& fusel oil. 

Properties of Alcohol. — Pure ethyl alcohol has a peculiar, 
pleasant odor. It remains liquid at very low tempera- 
tures, but has recently been converted into a solid at a 
temperature of — 130°. 5. It burns with a flame that 
does not deposit soot, and was hence formerly much used 
in laboratories for heating purposes, and is still used where 
gas cannot be obtained. Its effects upon the human 
system are well known. It intoxicates when taken in 
dilute form, while in large doses it is poisonous. It lowers 
the temperature of the body when taken internally, 
although it causes a sensation of warmth. 

Uses of Alcohol. — Alcohol is the principal solvent for 
organic substances. It is hence extensively used in the 
arts, as in the manufacture of varnishes, perfumes, and 
tinctures of drugs. The many beverages in use owe their 
intoxicating power to the presence of alcohol. The 
milder forms of beer contain from 2 to 3 per cent; light 
wines about 8 per cent; while whiskey, brandy, etc., 
sometimes contain as much as 60 to 75 per cent. 

Glycerin, CgllgOg. — Glycerin is an alcohol that occurs 
very widely distributed as a constituent of fats. The rela- 
tion it bears to the fats will be explained when the acids 



^34 THE ELEMENTS OE CHEMISTRY, 

that enter into the fats are taken up. It is obtained from 
the fats by boiling them with an alkali like, caustic soda or 
caustic potash, or by heating them with steam. 

Properties. — Glycerin is a thick, colorless liquid with a 
sweetish taste. It attracts moisture from the air, and is 
hence used to keep surfaces moist. 

Acids. 

Formic Acid, CH.O,. — This acid occurs in nature in red 
ants, in stinging-nettles, in the shoots of some of the 
varieties of pine, and elsewhere. It is a colorless liquid. 
DropjDed on the skin, it causes extreme pain and produces 
blisters. 

Acetic Acid, C2H^02. — This is the acid contained in 
vinegar which gives to it its value. It is formed from 
alcoholic liquids by exposing them to the air, in conse- 
quence of the presence of a microsco23ic organism which 
is contained in what is commonly known as ''^mother of 
vinegar. ^^ The formation of acetic acid from alcohol is 
due to the action of oxygen as represented in the equation 

C,H,0 + 0, = C,Hp, + H,0. 

Alcohol. Acetic acid. 

But oxygen alone does not effect the change. When the 
ferment is jDresent the oxidation takes place. Acetic acid 
is also obtained by distilling wood. Hence the names 
pyroligneoiis acid and tcood-vinegar. 

Properties. — Acetic acid is a clear, colorless liquid. It 
has a very penetrating, pleasant, acid odor, and a sharp 
taste. The pure substance acts upon the skin like formic 
acid, causing pain and raising blisters. 



SOME FAMILIAR COMPOUNDS OF CARBON. 235 

-Acetic acid is extensively used, chiefly in the 
dihite form known as vinegar. It is used in calico-print- 
ing in the form of iron and alumiiiinm salts. With iron 
it gives hydrogen, which is needed in the manufacture of 
certain compounds used in making dyes. 

Salts of Acetic Acid. — The best-known salts of acetic 
acid are lead acetate, Pb(C2H302)2^ commonly called sugai^' 
of lead; and copper acetate^ Cu(C2H302)2, a variety of 
which is known as verdigris. 

Fatty Acids. — Formic and acetic acids are the first 
members of an homologous series (see page 118). Some of 
the more important members are named in the following 

table : 

Formic acid CH2O2. 

Acetic *' C2H4O3. 

Propionic ** C3H9O2. 

Butyric '' C4H80a. 

Valeric '' CsHioOs. 

Palmitic '* C16H32O2. 

Stearic " CisHaeOa. 

They are called fatty acids for the reason that many of 
them are obtained from fats. 

Butyric Acid, C^Hg02 , is of special interest because it is 
obtained from butter by boiling with caustic potash. It 
occurs also in many other fats. There is a iiityric-acid 
ferment contained in putrid cheese which has the power 
of converting sugar into butyric acid. 

Palmitic Acid, CjgH3202, is obtained from many fats, 
but palm-oil is especially rich in it. 

Stearic Acid, C^gH3g02 , is the acid contained in the fat 
known as stearin. The so-called '^ stearin candles ^^ are 
made of a mixture of palmitic and stearic acids. 

Soaps. — Soaps are the alkali salts of the acids contained 
in fats, especially of palmitic and stearic acids. Fats are 



236 THE ELEMENTS OF CHEMISTRY. 

coinpounds of these acids with glycerin. When the fats 
are boiled with an alkali, as caustic soda^ the correspond- 
ing salts of the acids are formed, while the glycerin is set 
free. The palmitate and stearate of potassium and sodium 
are the soaps. 

Experiment 128. — In an iron pot boil a quarter of a pound of 
lard with a solutiou of 40 grams caustic soda in 250 c.c. of water 
for an hour or two. After cooling add a strong solution of 
sodium chloride. The soap formed will separate and rise to the 
top of the solution, where it will finally solidify. Dissolve some 
of the soap thus obtained in water. 

Use of Soap. — The cleansing power of soap depends upon 
the fact that it dissolves the oily film on the surface of the 
skin and thus facilitates the removal of the foreign sub- 
stances commonly known as dirt. 

Action of Soap on Hard Waters. — As has been explained, 
a hard water is one that contains salts in solution. Tem- 
porary liarchiess is that which is caused by calcium car- 
bonate held in solution in the water by carbon dioxide. 
Permanent hardness is caused by calcium sulphate or 
magnesium salts. The calcium and magnesium salts of 
palmitic and stearic acids are difficultly soluble in water. 
Therefore, when soap is added to a hard water these salts 
are precipitated, and give the water a hard feeling. In 
attempting to wash the hands with soap in a hard water 
they become covered with a thin layer of the insoluble 
salts which prevents them from rubbing freely over each 
other, and makes them feel sticky. Before the soap can 
do any good all the calcium must be precipitated. The 
action in the case of temporary hardness is represented by 
the equation 

2NaO,,H3,0, + CaCO, = Ca(C,H,0,), + Na^CO^. 

^. Soap. Calcium palmitate. 



SOME FAMILIAR COMPOUNDS OF CARBON, 237 

In the case of permanent hardness it is represented by 
the equation 

2NaC,,H,,0, + CaSO, = Ca(C,,H3,0,), + Na.SO,. 

Experiment 129. — Make some hard water by passing carbon 
dioxide through dihite lime-water until the precipitate first formed 
is dissolved again. Filter. Make a solution of soap by shaking up 
a few shavings of soap with water. Filter. Add the solution of 
soap to the hard water. Is a precipitate formed ? Rub a piece 
of soap between the hands wet with the hard water. 

Experiment 130. — Make some hard water by shaking 1 or 2 
litres of water with a little powdered gypsum. Perform with it 
the same experiments as those first performed with the water 
containing calcium carbonate. 

Soap and Civilization. — A great chemist and philosopher 
has said that the quantity of soap used in a country is a 
measure of the civilization of the country. Certain it is 
that soap is only used by civilized people, and that by 
them it is used in enormous quantities. In some farm- 
houses a primitive method for the manufacture of soap is 
practised, consisting in treating refuse fats with the lye 
extracted from wood-ashes. A soft soapy mass is thus 
obtained known as ^^ soft-soap. ^^ Fats form the starting- 
point in the manufacture of all soap. These are generally 
treated with caustic soda. Caustic soda is now largely 
made from sodium chloride by the action of an electric 
current (see page 182). 

Oxalic Acid, C2H20^. — This acid occurs very widely dis- 
tributed in nature, as in the sorrels, which owe their acid 
taste to the presence of acid potassium oxalate, KC^HO^; 
and as the ammonium salt in guano. It is probably one 
of the fiirst substances formed from carbon dioxide in the 
plant. It can be manufactured by heating wood shavings 



238 THE ELEMENTS OF CHEMISTRY. 

or sawdust with caustic soda and caustic potash. Oxalic 
acid is an active poison. It is used in calico-printing, and 
in cleaning brass and copper surfaces. 

Lactic Acid, CgHgOg. — Lactic acid is made by the fer- 
mentation of sugar by means of the lactic-acid ferment. 
The reaction effected by the ferment is represented by the 
equation 

Malic Acid, C^HgO^. — This acid is very widely dis- 
tributed in the yegetable kingdom, as in apples, cherries, 
etc. 

Tartaric Acid, C^HgOg. — Tartaric acid occurs very widely 
distributed in fruits, sometimes uncombined, sometimes 
in the form of the potassium or calcium salt; as, for 
example, in grapes, berries of the mountain-ash, potatoes, 
cucumbers, etc., etc. It is prepared from ^^ cream of 
tartar. ^^ This is acid potassium tartrate, which is formed 
when grape-juice ferments. 

Citric Acid, CgHgO^. — Citric acid, like malic and tartaric 
acids, is very widely distributed in nature in many varieties 
of fruit, especially in lemons. It is also found in currants, 
whortleberries, raspberries, goosebe^Ties, etc., etc. It is 
prepared from lemon-juice: 100 parts of lemons yield 5-J- 
parts of the acid. It is a solid, crystallized substance, 
soluble in water. It is sometimes used for the purpose of 
making lemonade without lemons, and there is no objec- 
tion to its use for this purpose. 

Ethers. . 

Ether, C^H^^O. — Ordinary ether is the best-known repre- 
sentative of the class of compounds called ethers. It is 



SOME FAMILIAR COMPOUNDS OF CARBON, 239 

formed from ordinary alcohol by treating it with sulphuric 
acid and distilling. The action is represented by the 
equation 

2C,H,0 = C,H,„0 + H,0. 

Alcohol. Ether. 

Ether is a liquid which boils afc a low temperature and 
takes fire and burns readily. Inhaled it produces insensi- 
bility to pain. It is therefore called an ancestlietic. 

Ethereal Salts. 

Action of Acids upon Alcohols. — When an acid acts 
upon an alcohol it is neutralized, though not as readily as 
when it acts upon a base. The product is a substance 
that resembles a salt and is called an ethereal salt. Thus 
when nitric acid acts upon alcohol this reaction takes place : 

0,H,0 + HNO3 = C,H,NO, + H,0. 

The product C2II5NO3, called ethyl nitrate, is an 
ethereal salt. The alcohol acts as if it were a substance 
like caustic potash and made up thus, C^H^-OH. The 
resemblance between its action and that of caustic potash 
is shown by the equations 

KOH + HNO3 r=: KNO3 + H,0, and 
C,H,OH + HNO3 ^ C,H,N03 + H,0. 

Saponification. — When an ethereal salt is boiled with a 
caustic alkali it is decomposed, the products being an 
alcohol and an alkali salt. Thus when ethyl nitrate is 
boiled with caustic potash, potassium nitrate and alcohol 
are formed: 

C.H.NO, + KOH ^ C,H,OH + KNO3. 



240 THE ELEMENTS OF CHEMISTRY, 

This process is called saponification^ because the most 
important example is furnished by soap-making. 

Fats. — The fats are ethereal salts in the formation of 
which glycerin, as the alcohol, and three acids take part. 
The three acids are palmitic and stearic acids, already 
mentioned, and oleic acid, CjgH3^02. Although the com- 
position of these substances is comparatively complex, the 
way they act upon one another is simple, and is the same 
as the action of nitric acid upon alcohol in forming ethyl 
nitrate. The fats, then, are the palmitate, stearate, and 
oleate of glyceryl, C3H5, which bears to glycerin very much 
the same relation that etliyl, CJI^, bears to alcohol. 
When a fat is boiled with caustic soda, the sodium salts of 
the acids, contained in the fat, and glycerin are formed. 

Butter consists of ethereal salts of glycerin and several 
fatty acids, among which are palmitic, stearic, and butyric 
acids. Oleo-margarin is an artificial butter made from 
other fats than that from milk. 

Ethereal Salts as Essences. — The ethereal salts generally 
have pleasant odors, and it is to their presence that many 
fruits owe their flavors. Some of the compounds are now 
made artificially and used instead of the natural extract of 
the fruit. Thus the ethyl salt of lutyric acid is used 
under the name of essence of 'pineapples, and the amyl salt 
of valeric acid under the name essence of apples. 

Nitroglycerin. — Among the more important ethereal 
salts of glycerin are the nitrates. Two of these are known, 

( NO3 

viz., the mono-nitrate, C3H. -< OH > and the tri-nitrate, 

i OH 

C3H5(N03)3, the latter being the chief constituent of 

nitroglycerin. Nitroglycerin is prepared by treating 



SOME FAMILIAR COMPOUNDS OF CARBON. 241 

glycerin with a mixture of concentrated sulphuric and 
nitric acids. It is a pale j^ellow oil which is insoluble in 
water. At — 20° it crystallizes in needles. It explodes 
very violently by concussion. It may be burned in an 
open vessel, but if heated above 250° it explodes. Dyna- 
mite is infusorial earth '^ impregnated with nitroglycerin. 
Nitroglycerin is the active constituent of a number of 
explosives. 

Eelations between the Compounds Coksidered. 

Comparison of the Formulas. — On comparing the for- 
mulas of the hydrocarbons of the marsh-gas series (see page 
117) with those of the simplest alcohols and the fatty 
acids, it will be seen that these compounds are all related 
in a simple way. Below are lists of a few of the hydro- 
carbons, alcohols, and acids : 



Hydrocarbons. 


Alcohols. 
CH,0 




Acids. 


C.H, 


C.H,0 




C^H^O, . 


C.H3 


CsH^O 




CsH.O, 


0,H„, etc. 


C.H,0, 


etc. 


C,H,0,, etc, 



Each of these series is an homologous series. 

Alcohols. — Alcohols have been shown to be derived from 
the hydrocarbons by the substitution of hydroxyl, OH, 
for one or more hydrogen atoms, or from water by substi- 
tuting a group of atoms consisting of carbon and hydrogen 
for one of the hydrogen atoms of the water. An alcohol, 

* That is to say, earth made up of the microscopic flinty shells 
which constitute the fossil remains of certain minute and simple 
plants. 



242 THE ELEMENTS OF CHEMISTRY. 

then, is a hydroxide, just as a metallic base is; only, 
instead of consisting of a metal in combination with 
hydroxyl, it consists of a group of atoms of carbon and 
hydrogen in combination with hydroxyl. Thus : 

Metallic Bases. Alcohols. 

K(OH) CH3(0H) 

Na(OH) C,H.(OH) 

More Complex Alcohols. — Just as lime is a more complex 
base than caustic potash, as shown by the formulas KOH 
and Ca(0H)2, so there are more complex alcohols than 
ordinary alcohol. A good example is furnished by 
glycerin, CgHgOg , which has been shown to be a hydroxide 
corresponding to aluminium hydroxide, A1(0H)3, a fact 
which is represented by the formula 63115(011)3. It may 
be called glyceryl hydroxide, the complex, C3H5, being 
known as glyceryl. 

Radicals or Residues. — The groups of atoms of hydrogen 
and carbon contained in the alcohols are called radicals or 
residues. So we may say that an alcohol is water in which 
a radical has been substituted for half of the hydrogen. 



HOH 


0,H,OH 


Water. 


Ordinary alcohol. 


HOH 


roH 


HOH 


O3H, ] OH = C3H3O, 


HOH 


(oh 


Water. 


Glycerin. 



Acids. — Just as the alcohols have been shown to be 
derived from water, so the organic acids have been shown 
to be derived from carbonic acid. Carbonic acid itself is 
not known. But the carbonates are derived from an acid 



SOME FAMILIAR COMPOUNDS OF CARBON. 243 

of the formula H^COj, or CO \ ^u- If? i^i ^his acid, a 
radical, as, for example, ethyl, CjH^, is substituted for a 

{fy TT 
^2 5 or CjHgOj 

is the result. If methyl, CH3 , instead of ethyl is substi- 
tuted for the hydroxyl, the product is CO \ ^tt^ or C2H^02, 

which is acetic acid. In a similar way all the organic 
acids are believed to be derived from carbonic acid. 



CHAPTEE XXVI. 
OTHER COMPGUISTDS OF CARBON. 

The Carbohydrates. — The carbohydrates form an impor- 
tant group of carhon compounds which includes the most 
abundant substances found in the vegetable kingdom. 
Besides carbon they contain hydrogen and oxygen generally 
in the proportion to form water. Hence they are called 
carbohydrates. The chief compounds included under this 
head are grape-sugar or glucose^ fructose (or levulose)^ 
maltose^ cane-sugar^ starchy cellulose^ gum, and dextrin. 

Grape-sugar, Glucose, Dextrose, CgHj^Og. — Dextrose 
occurs very widely distributed in the vegetable kingdom^ 
particularly in sweet fruits. It is found also in honey 
and, further, in the liver and the blood. 

rormation of Dextrose. — Dextrose or glucose is formed 
from several of the carbohydrates by boiling with dilute 
mineral acids, or by the action of ferments. Its formation 
from cane-sugar takes place according to this equation, 
equal quantities of dextrose and fructose being formed: 

Cane-sugar. Dextrose. Fructose. 

Its formation from starch is represented by this equation : 



Starch. Dextrose. 



244 



OTHER COMPOUNDS OF CARBON. 245 

Manufacture of Dextrose or Glucose. — Dextrose is pre- 
pared on the large scale from corn-starch in the United 
States, and from potato-starch in Germany. The change 
is usually effected by boiling with dilute sulphuric acid. 
The acid is afterwards removed by treating with chalk, 
and filtering. [Explain how this removes the acid.] The 
filtered solutions are evaporated either to a syrupy con- 
sistency, and sent into the market under the names 
^^ glucose, ^^ ^^ mixing-syrup,'^ etc., or to dryness, the solid 
product being known as ^^ grape-sugar.^^ 

Properties. — Dextrose crystallizes from concentrated 
solutions, and as seen in commercial ^^ granulated grape- 
sugar ^^ looks very much like granulated cane-sugar. It is 
sweet, but not as sweet as cane-sugar. It is estimated that 
the sweetness of dextrose is to that of cane-sugar as 3 : 5. 
Under the influence of yeast it ferments, yielding mainly 
alcohol and carbon dioxide. Putrid cheese transforms it 
into lactic acid, and then into butyric acid. 

Levulose {Fruit-sugar), Q^^fi^, — This form of sugar 
occurs with dextrose in fruits; and is formed by the action 
of dilute acids or ferments on cane-sugar, which breaks 
down according to the equation 

Cane-sugar. Dextrose. Levulose. 

As cane-sugar is found in unripe fruits, it is probable 
that the change represented in the equation takes place 
during the process of ripening. 

Cane-sugar, 0^211220^^. — This well-known variety of 
sugar occurs widely distributed in nature — in sugar-cane, 
sorghum, the Java palm, the sugar-maple, beets, madder- 



246 THE ELEMENTS OF CHEMISTRY. 

root^ coffee, walnuts, liazel-nuts, sweet and bitter almonds; 
in the blossoms of many plants, etc., etc. 

Sugar-refining. — Sugar is obtained mainly from the 
sugar-cane and beets. In either case the processes of 
extraction and refining are largely mechanical. When 
sugar-cane is used, this is macerated with water to dissolve 
the sugar. Thus a dark-colored solution is obtained. 
This is evaporated, and then passed through filters of 
bone-black by which the color is removed. The clear 
solution is then evaporated in open vessels to some extent; 
and, finally, in large closed vessels called ^^ vacuum- pans, ^^ 
from which the air is partly exhausted, so that the boiling 
takes place at a lower temperature than would be required 
under the ordinary pressure of the atmosphere. The 
mixture of crystals and mother-liquors obtained from the 
" vacuum-pans '' is freed from the liquid by being brought 
into the ^^ centrifugals/^ These are funnel-shaped sieves 
which are revolved rapidly, the liquid being thus thrown 
by centrifugal force through the openings of the sieve, 
while the crystals remain behind and are thus nearly dried. 
The final drying is effected by placing the crystals in a 
warm room. 

Molasses. — The mother-liquors obtained from the '' cen- 
trifugals '' are further evaporated, and yield lower grades 
of sugar; and, finally, a syrup is obtained which does not 
crystallize. This is molasses. 

Properties of Sugar. — Sugar crystallizes from water in 
large well-formed prisms. When heated to 210° to 220°, 
it loses water, and is converted into a substance called 
caramel^ which is more or less brown in color. When 
boiled with dilute acids, cane-sugar is split into equal 



OTHER COMPOUNDS OF CARBON. 247 

parts of dextrose and levulose. The mixture of the two is 
called invert-sugar. Yeast gradually transforms cane- 
sugar into dextrose and levulose^ and these then undergo 
fermentation. Cane-sugar does not ferment. 

Sugar of Milk, lactose, 0^21X220^^ + HgO.— This sugar 
occurs in the milk of all mammals. It is obtained in the 
manufacture of cheese. Cows^ milk consists of water, 
casein, butter, sugar of milk, and a little inorganic 
material, in about the following proportions : 

Water .... 87 per cent. 

Casein 4 '* 

Butter ^3 

Sugar of milk 4J *' 

Mineral matter | '' 

100 

Cheese is made by adding rennet to the milk, which 
causes the separation of the casein. The sugar of milk 
remains in solution, is separated by evaporation, and 
purified by recrystallization. It has a slightly sweet taste, 
and is much less soluble in water than cane-sugar. 

Souring of Milk. — Sugar of milk ferments under certain 
circumstances, and is transformed mostly into lactic acid. 
The souring of milk is a result of this fermetitation. The 
lactic acid formed coagulates the casein, that is to say, 
causes it to appear in insoluble semi-solid form. 

Cellulose, CgHi^Og. — Cellulose forms, as it were, the 
groundwork of all vegetable tissues. It presents different 
appearances and different properties, according to the 
source from which it is obtained; but these differences are 
due to substances with which the cellulose is mixed ; and 
when they are removed, the cellulose left behind appears 
to be the same thing, no matter what its source may have 



2 43 THE ELEMENTS OF CHEMISTRY. 

been. The coarse wood of trees and the tender shoots of 
the most delicate plants consist essentially of cellulose. 
Cotton-wool, hemp, and flax consist almost wholly of 
cellulose. 

Properties. — Cellulose does not easily crystallize, and is 
insoluble in all ordinary solvents. It dissolves in concen- 
trated sulphuric acid. If the solution is diluted and 
boiled, the cellulose is converted into dextrin and dextrose. 
It will thus be seen that rags, paper, and wood, all of which 
consist largely of cellulose, might be used for the prepara- 
tion of dextrose or glucose, and consequently of alcohol. 

Gun-cotton, Pyroxylin, Nitro-cellulose. — Cellulose has 
some of the properties of alcohols ; among them the power 
to form ethereal salts with acids. Thus, when treated 
with nitric acid it forms several nitrates, just as glycerin 
forms the nitrates known as nitro-glycerin (which see). 
The nitrates are explosive, and are used for blasting under 
the name gun-cotton. 

Collodion. — A solution of gun-cotton in a mixture of 
ether and alcohol is known as collodion solution, which is 
much used in photography. When poured upon any sur- 
face, such as glass, the ether and alcohol rapidly evaporate, 
leaving a thin coating of the nitrates. 

Celluloid. — Celluloid is an intimate mixture of gun- 
cotton and camphor. As it is plastic at a slightly elevated 
temperature, it can easily be moulded into any desired 
shape. When cooled it hardens. 

Paper. — Paper in its many forms consists mainly of 
cellulose. The essential features in the manufacture of 
paper are, first, the disintegration of the substances used. 
This is effected partly mechanically and partly by boiling 



OTHER COMPOUNDS OF CARBON. 249 

with caustic soda or with acid sodium sulphite. Then the 
resulting mass is converted into pulp by means of knives 
placed on rollers. The pulp, with the necessary quantity 
of water, is then passed between rollers. Chiefly rags of 
cotton or linen are used in the manufacture of paper; 
wood and straw are also used. 

Starch, CgHj^-O^. — Starch is found everywhere in the 
vegetable kingdom in large quantity, particularly in all 
kinds of grain, as maize, wheat, etc. ; in tubers, as the 
potato, arrowroot, etc. ; in fruits, as chestnuts, acorns, etc. 

Manufacture of Starch. — In the United States starch is 
manufactured mainly from maize; in Europe, from 
potatoes. The processes made use of are mostly mechani- 
cal. The maize is first treated with warm water; the 
softened grain is then ground between stones, a stream of 
water running constantly into the mill. The thin paste 
which is carried away is brought upon sieves of silk bolt- 
ing-cloth, which are kept in constant motion. The starch 
passes through with the water as a milky fluid. This is 
allowed to settle when the water is drawn off. The starch 
is next treated with water containing a little alkali, the 
object of which is to dissolve gluten, oil, etc. The mix- 
ture is now brought into shallow, long wooden runs, where 
the starch is deposited, the alkaline water running off. 
Finally, the starch is washed with water, and dried at a 
low temperature. 

Properties. — Starch in its usual condition is insoluble in 
water. If ground with cold water it is partly dissolved. 
If heated with water the membranes of the cells of which 
the starch is composed are broken, and the contents form 
a partial solution. On cooling, it forms a transparent 



2 go THE ELEMENTS OF CHEMISTRY, 

jelly called starch-paste. By dilute acids and ferments 
starch is converted into dextrin^ maltose^ and dextrose. 

Flour. — Wheat flour, which may serve as an example of 
flour in general, contains water, starch with a little sugar 
and gum, gluten, and a small quantity of mineral matter. 
The flnest flour contains about 10 per cent of gluten and 
70 per cent of starch. Gluten is a substance that resem- 
bles in many respects the white of eggs, or egg-albumin. 

Bread-making. — The chemical changes that take place 
in bread-making are of special interest. Bread is made 
by mixing the flour with water and a little yeast. The 
dough thus prepared is put in a warm place for a time, 
when it inses. The rising is a result of fermentation 
caused by the yeast. A part of the starch contained in 
the flour is converted into sugar, and this is then converted 
into alcohol and carbon dioxide by fermentation. In 
striving to escape from the thick gummy dough the carbon 
dio:Jide flUs it with bubbles of gas, making it light and 
porous. When the loaf is put into the oven the gases 
contained in it expand, making it still lighter, and the 
alcohol passes off; then the fermentation is checked and 
no further chemical change takes place except on the 
surface where the substances are partly decomposed and 
converted into a dark-colored product, the crust. 

A Few Compoukds feom Coal-tak. 

Aromatic Compounds. — The fact that benzene, CgHg, 
toluene^ G^'K^ , and other hydrocarbons are obtained from 
coal-tar has already been mentioned (p. 230). These 
hydrocarbons are the starting-points for the preparation 
of a large number of compounds of carbon that are com- 



OTHER COMPOUNDS OF CARBON, 251 

monly called the ^' aromatic compounds/^ as many of them 
have a pleasant aromatic odor. 

Nitrobenzene, Cgn,]Sr02. — This substance is formed by 
treating benzene with nitric acid : 

It is a yellow liquid with a pleasant odor like that of the 
oil of bitter almonds. It is much used under the name 
artificial oil of hitter ahnonds. 

Aniline, CgH^NHg. — When nitrobenzene is treated with 
nascent hydrogen the oxygen is extracted and hydrogen 
takes its place : 

C,H,NO, + 6H = C,H,NH, + 2H,0. 

The product is the substance known as aniline. It is a 
colorless liquid. When treated with mercuric chloride 
(corrosive sublimate, HgCl2) or arsenic acid commercial 
aniline is converted into the dye magenta, which is the 
substance from which the aniline dyes are prepared. 

Aniline Dyes. — Of these a large number are in use. 
They are all derivatives of rosaniline, of which magenta is 
a salt. Aniline dyes of a great many different colors are 
made, some of them of great beauty. 

Phenol, Carbolic Acid, CgHgO. — This familiar substance 
is contained in coal-tar, and is extracted from it by treat- 
,ing with caustic soda in which the carbolic acid dissolves. 
When pure it crystallizes in beautiful, colorless, rhombic 
needles. It has a peculiar, penetrating odor, and is 
poisonous. It is much used as a disinfectant. 

Oil of Bitter Almonds, 



^ ..,,,, 1 C.H^O. — This substance occurs 

Benzoic Aldehyde, ( ^ ^ 

in combination in amygdalin, which is found in bitter 



252 THE ELEMENTS OF CHEMISTRY, 

almonds, laurel-leaves, cherry-kernels, etc. Amygdalin 
belongs to tlie class of compounds known . as glucosides, 
which break up into glucose and other substances. 
Amygdalin itself, under the influence of emidsin, which 
occurs with it in the plants, breaks up into oil of bitter 
almonds, hydrocyanic acid, and dextrose : 

C,„H,,NO,, + 3H,0 = C,H,0 + CNH + 2C,H,0,. 

Amygdalin. Oil of Hydrocy- Glucose, 

bitter anic acid, 

almonds. 

It is prepared from bitter almonds, which yield about 
1. 5 to 2 per cent. It is a liquid which has a pleasant 
odor. It is made artificially from coal-tar, and is used in 
the preparation of artificial indigo. 

Benzoic Acid, C^IIgOg. — Benzoic acid occurs in gum 
benzoin and in the balsams of Peru and Tolu, and is made 
artificially from coal-tar by oxidizing toluene,* C^Hg. 

Balsams and Odoriferous Resins. — The balsams of Peru 
and Tolu are thick fragrant fiuids that are obtained from 
certain trees in South America and elsewhere by cutting 
the bark. Benzoin is a similar substance. These as well 
as myrrh, frankincense, and other substances of the kind 
are used for their odors. The odors are increased when 
the substances are heated. Hence they are largely used 
as incense. 

Gallic Acid, C^HgO,. — Gallic acid occurs in sumach, in 
Chinese tea, and many other plants. It is formed by 
boiling tannin or tannic acid with sulphuric acid. It is 
prepared from gall-nuts by fermentation of the tannin 

* The name toluene comes from the fact that this hydrocarbon 
was first obtained from the balsam of Tolu. 



OTHER COMPOUNDS OF CARBON, 253 

contained in them. It is closely related to tannin or 
tannic acid. 

Tannic Acid, Tannin, C^JI^oOg. — This substance occurs 
in gallnuts, from which it is extracted in large quantities. 
It is soluble in water. Its solution gives a dark blue-black 
color with iron salts. Tannin is used extensively in medi- 
cine, in dyeing, in the manufacture of leather and of ink. 

Experiment 131. — Boil 10 grams of powdered gallnuts with 
60 c.c. of water, adding water from time to time. A solution of 
tannin is thus obtained. Filter after standing. In a test-tube 
add to some of this solution a few drops of a solution of copperas 
(ferrous sulphate). A colored precipitate is formed which gradu- 
ally changes to black. 

Tanning. — The process of tanning consists in treating 
hides from which the hair has been removed with an 
infusion of hemlock or oak bark, or of sumach leaves, in 
which there is tannic acid. The acid combines with 
certain parts of the hides, forming insoluble compounds 
which remain in the pores, converting the hides into 
leather. 

Indigo. — In several plants which grow in the East and 
West Indies, in South America, Egypt, and other warm 
countries, occurs a substance called indican which, when 
treated with dilute mineral acids and certain ferments, 
breaks up into indigo-blue and a substance resembling 
glucose. Commercial indigo contains as its principal 
ingredient indigo-blue. Indigo-blue is now prepared 
artificially. 

Naphthalene, C^^Hg. — This is a hydrocarbon which is 
contained in coal-tar in large quantity. It is a beautiful 
white crystallized substance much used in the preparation 



2 54 THE ELEMENTS OF CHEMISTRY, 

of dyes. The so-called ^' moth-balls '' consist of naph- 
thalene. 

Anthracene, Cj^Hj^. — Anthracene like naphthalene is 
obtained from coal-tar. Its chief use is in the preparation 
of artificial alizarin. 

Alizarin, Cj^HgO^. — Alizarin is the well-known dye that 
was formerly obtained from madder-root. For some years 
it has been made artificially from anthracene, and the 
cultivation of madder has been largely given up. Madder- 
root was used for dyeing " Turkey red.^^ Artificial alizarin 
is almost exclusively used for this purpose at present. 



Glucosides. — Glucosides are certain natural substances 
that break down under the influence of ferments and 
dilute acids into sugar and other compounds. Amygdalin 
has already been mentioned. This breaks down into oil 
of bitter almonds and dextrose. Indican, which yields 
indigo and dextrose, is another example. 

Myronic Acid, another glucoside, is found in the form 
of the potassium salt in black mustard-seed. When 
treated with myrosin, which is contained in the aqueous 
extract of white mustard-seed, potassium myronate is con- 
verted into dextrose and oil of mustard. 

Alkaloids. — These are compounds occurring in plants, 
frequently being those parts of the plants that are most 
active when taken into the animal body. They are hence 
sometimes called the active principles of plants. Many of 
these substances are used in medicine. They all contain 
nitrogen and in some respects resemble ammonia. Only 
a few of the more important alkaloids need be mentioned 
here. 



OTHER COMPOUDNS OF CARBON, 255 

ftuinine. — This valuable alkaloid is obtained from the 
outer bark of certain trees that grow in Peru. The bark 
is known as Peruvian bark. 

Cocaine is found in cocoa-leaves. Its hydrochloric-acid 
salt has come into prominence in medicine, owing to the 
fact that a small quantity of its solution placed upon the 
eye or the gums or injected beneath the skin causes 
insensibility to pain. 

Nicotine occurs in tobacco-leaves in combination with 
malic acid. 

Morphine and Narcotine are the principal alkaloids 
found in opium, which is the evaporated sap that flows 
from incisions in the capsules of the white poppy before 
they are ripe. 



QUESTIONS AND PROBLEMS. 



CHAPTEK I. 

What two kinds of changes are you familiar with? 

Give some familiar illustrations of each. 

What is the chief difference between the two kinds of change? 

Mention some examples of physical changes which are not given 
in the book. 

Mention some examples of chemical changes not given in the 
book. Why do you call these changes chemical changes? 

What is meant by saying that physical and chemical changes 
are related? 

Give some familiar examples which make these relations clear. 

How does the steam-engine illustrate these relations? 

Suppose a stone should fall upon some gunpowder and cause it 
to explode, which would be physical and which chemical change? 

Give some examples showing that heat can cause chemical 
changes. 

Give some examples showing that chemical changes can pro- 
duce heat. 

Give examples showing that in some cases when substances are 
simply brought together chemical changes are caused. 

Give some examples showing that solution aids chemical action. 

How can we distinguish chemical action from all other kinds 
of action? 

What is the difference between a mixture and a chemical com- 
pound ? 

How can this difference be illustrated by means of iron and 
sulphur ? 

Suppose sugar and sand were placed together in a vessel and 
well shaken up, would a chemical compound or a mechanical 
mixture be formed? Try the experiment, and see whether you 
can answer the question with the aid of the experiment. Treat 
the substance with water; what takes place? What is left? 

WTien iron and sulphur combine chemically, is there any gain 
or loss in weight ? 

Explain the difference between elements and compounds. 

Is wood an element? Whjt 

256 



QUESTIONS AND PROBLEMS. 257 

Is the number of compounds larger than the number of ele- 
ments? 

How many elements enter into the composition of the things 
with which we generally have to deal? 

Give some examples of elements. Why are they called ele- 
ments? 

Give some examples of compounds. Why are they called com- 
pounds? 

In general, what is meant by chemical action? 

What three kinds of chemical action are there? Give examples 
of each. 

Why does a stone fall to the earth when thrown upward? 

Wliy do substances act chemically upon one another? 

Suppose chemical attraction should cease, what would be the 
result ? 

Which of the elements is most abundant? Which comes next 
in order? 

Which is the principal element that enters into the composition 
of living things? 

How are the names of the elements formed? Give examples. 

What is meant by the symbols of the elements? 



CHAPTER II. 

Describe the changes which are produced in lead, zinc, and tin 
by heating them, and describe the experiments which taught you 
what these changes are. 

How did you learn that the air had anything to do with these 
changes ? 

Did heat have anything to do with the changes? Suppose you 
knew that the bits of metal used in Experiments 13, 14, and 15 
increased in weight when heated in the air, and that they did 
not increase in weight when heated so that the air could not get 
at them, what would that show? 

What familiar facts show that the air has something to do with 
burning? 

How could you find out what the air does when things burn 
in it? 

What is noticed when a candle is burned in a closed vessel? 

When a candle burns is there a gain or loss of matter? 

How much of the air is used up when anything burns in a 
closed vessel? 

Suppose a substance is burned in a closed vessel containing air 
and gains 5 grams in weight, where would this 5 grams of matter 
come from? How much would you expect to find that the air 
had lost in weight? 

What IS the composition of the air? 

Why are oxygen and nitrogen called elements? 



258 THE ELEMENTS OF CHEMISTRY. 



CHAPTER III. 

Where and in what quantity is oxygen found? 

How can we get oxygen from the air? 

Explain how oxygen is collected when it is set free from the 
oxide of mercuiy. 

What other ways are there of getting oxygen? 

What is the appearance of oxygen? Its smell? taste? What 
happens to it when it is much cooled down and compressed? 

How does oxygen behave towards other substances at the ordi- 
nary temperature? How do you know this? Does oxygen act 
upon anything at the ordinary temperature? Give examples. 

Of what importance is oxygen to all animals? What dilference 
is there between the action of oxygen at the ordinary tempera- 
ture and at higher temperatures? How did you learn this differ- 
ence? 

When substances burn in oxygen, is the oxygen used up ? What 
becomes of it? Do the substances gain or lose in weight? How 
does the weight of the oxygen used up compare with the gain in 
weight of the substance burned? 

What does burning in oxygen consist in? 

Is burning in the air the same chemical act as burning in 
oxygen? How can this be proved? Why do substances not burn 
as actively in the air as they do in oxygen? 

What is meant by combustion? 

What are combustible substances? 

What are incombustible substances? 

Is water combustible? Is wood combustible? 

Give an example of a substance which will not burn in the air, 
but which will burn in oxygen. How was this shown? 

What is meant by the kindling temperature? Explain why it 
is that a stick of wood burns gradually and not all at once. 

Explain the connection between the heat and light produced, 
and the combustion of a substance. 

What is meant by the expressions chemical work and chemical 
energy f 

Do combustible substances possess chemical energy? 

Show how a combustible substance can do work. What are the 
substances called Avhich are formed in combustion? Give examples. 

CHAPTER IV. 

Explain what is meant by saying that the elements combine in 
definite weights. 

What is the law of definite proportions? 

How are natural laws discovered? 

What is a natural law? 

In studying the proportions by weight in which the elements 
combine with one another, what is observed? 

What are the combining weights of the elements? 



; QUESTIONS AND PROBLEMS. 259 

How is a cliemicj/l compound expressed by a symbol? 

What does the symbol NaCl mean? What does stand for? 
What does Fe stand for? 

How does alchemist express what takes place when mercury 
oxide is heated? 

How much mercury is contained in 20 grams of mercury oxide? 

How much oxygen is contained in 30 grams of mercury oxide? 

How much mercury oxide would be necessary to furnish 10 
grams of oxygen? 

How much mercury oxide would be necessary to furnish 10 
grams of mercury? 

Explain what is meant by the law of multiple proportions. Give 
examples illustrating the law. 
'What do the symbols SOo , CO^ , and H^SO^ mean ? 

CHAPTER V. 

Where and in what forms is nitrogen found in nature? 

How can we get nitrogen from the air? 

Why do we use phosphorus for the purpose? 

Describe the method of preparing nitrogen. 

How can nitrogen be obtained from the air by the use of copper? 

What is the color of nitrogen? its taste? its odor? How does 
it differ from oxygen in its conduct towards burning things? 
Could animals live in it? Why? Suppose there were no nitrogen 
in the air, how would our fires differ from the fires in the air as it 
is now? 

What is the difference between a chemical compound and a 
mechanical mixture? 

Are nitrogen and oxygen chemically combined or mixed together 
in the air? What reasons can you give for your statement? 

How is liquid air obtained? 

How is oxygen obtained from it? 

What is argon? Why was that name given to it? 
CHAPTER VI. 

How can it be shown that water is contained in, wood? in meat? 

Is water present in large or small proportion in animal and 
vegetable substances. 

What is meant by water of crystallization? 

What are efflorescent substances? 

What are deliquescent substances? 

Is water an element or a compound? How do you know? 

Describe the experiment in which an electric current is passed 
through water. What does the experiment show? 

CHAPTER VII. 

Where and in what forms is hydrogen met with in nature? 
How is hydrogen obtained? 

What takes place when a piece of sodium is thrown upon water? 
What takes place when steam is passed over heated iron? 



26o THE ELEMENTS OF CHEMfSTRY. 

"What is water-gas, and how is it obtained? ^ 

Which are the common acids? What do they all contain? What 
takes place when they are treated with metallic elements? 

What is the most convenient method for preparing hydrogen? 

Describe the process fully, and show how you can collect the hy- 
drogen. 

How can it be purified? 

What are the properties of hydrogen ? 

How is it shown that hydrogen is lighter than air? 

What relation is there between the weights of equal volumes of 
hydrogen and oxygen? 

If the weight of a certain bulk of hydrogen is 1 ounce, what 
would be the weight of the same bulk of o-xygen? 

What relation is there between the combining weights of hydro- 
gen and oxygen and the weights of equal bulks of the two gases? 

When ^\e say that the combining weight of hydrogen is 1 and 
that of oxygen 16, what is meant? What is meant when we say 
the combining weight of iron is dQ^. 

If we should call the combining weight of oxygen 100, what 
would be the combining weight of hydrogen? 

What change' takes place in hydrogen when it is cooled down 
very much and greatl}^ compressed? 

Does hydrogen combine with oxygen at the ordinary tempera- 
ture? How do you know? 

What takes place when it is heated in oxygen? 

Does hydrogen support combustion? How can this be shown? 



CHAPTER Vni. 

What is formed when hydrogen burns? How can this be shown? 
How is it explained? 

What takes place when a flame or spark is applied to a mixture 
of hydrogen and oxygen? How is this explained? 

How can we show what takes place when a mixture of hydrogen 
and oxygen explodes? What has been shown to take place? How 
does this help us to understand what the composition of water is? 

In what other way can the composition of water be found out ? 

Explain exactly how the experiment with copper oxide teaches 
us what the composition of water is. 

What is meant by reduction? a reducing agent? 

Explain the oxyhydrogen blowpipe and its uses. 

Explain the lime-light or Drummond light. 

Has water any color? 

Is the water which is found in nature pure? Why is this? 

Why does ice float on water? 

What is the purest water found in nature? Why? 

What is the character of the water found in mountain streams 
which flow over sand-stone? Why? 

What is the character of the water which flows over limestone? 

WTiat are mineral springs? 



QUESTIONS AND PROBLEMS, 261 

How does waW become salt? 

What are effervescent waters? chalybeate waters?. What is sul- 
phur water? 

What are the most common causes of impurities in water? 

What change takes place in river-water which has been contam- 
inated with sewage? 

What precautions should be taken in regard to the position of 
wells? Why? 

How can water be purified? Describe the process of distillation. 

What kinds of substances cannot be removed from water by dis- 
tillation? 

What is meant by saying that water is the best solvent? 

Why do we use solutions in studying the chemical action of sub- 
stances upon one another? 

What is a solution? 

What is expressed by the symbol HoO ? 

In what respects do hydrogen and oxygen resemble each other? 
In what respects do they differ from each other? 

Do hydrogen and oxygen combine readily? Does combination 
take place more readily between those elements which are alike or 
between those which are unlike? 

AATiat change takes place in oxygen when electric sparks are 
passed through it? In what other ways can this change be 
brought about? 

How can ozone be converted into oxygen? 

When oxygen is changed to ozone, and ozone to oxygen, is there 
any change in weight? 

What is hydrogen dioxide? How is it made? What is its most 
striking property? What is it used for? 

CHAPTER IX. 

What is destructive distillation? 

From what kinds of substances is ammonia given o-ff in destruc- 
tive distillation? 

"WTiat is one of the products formed when substances containmg 
carbon, hydrogen, and oxygen are heated? In what experiment 
which you have already performed is this shown? 

Explain why ammonia is formed in gas-works? 

What does the process of decay consist in? 

What becomes of the nitrogen contained in animal substances 
when they decay? 

What connection is there between saltpetre and nitric acid? be- 
tween potassium nitrite and nitrous acid? 

What is the " ammoniacal liquor" of the gas-works? What is 
formed when hydrochloric acid is added to this liquor? 

How is ammonia obtained from ammonium chloride? 

Express what takes place in a chemical equation, and explam 
exactly what the equation means. 

[The expression 2XH4CI represents twice the quantity of am- 



262 THE ELEMENTS OF CHEMISTRY. 

monium chloride that is represented by NH4CI. So also 2XH3 
represents a quantity of ammonia twice as great as that represented 
by NH,.] 

How much ammonia can be obtained from 50 grams of am- 
monium chloride? 

The combining weight of nitrogen is 14, that of calcium, Ca, is 
40, and that of chlorine, CI, is 35.5. We have, therefore, these 
relations : 

2NEI^C1 + CaO = 2NH3 + CaCl2 + H2O 

3(14 + 4 + 35.5) + (40 + 16) = 2(14 + 3) + (40 + 71) + (2+16) 



2 X 53.5 + 56 r:r 2 X 17 + 111 + 18 

107 + 56 = 34 + 111 + 18 

To determine the quantity of ammonia which can be obtained 
from 50 grams of ammonium chloride, we have simply to solve 
the proportion 

107 : 34 : : 50 : the weight of ammonia. 

For from 107 parts by weight of ammonium chloride there are 
formed 34 parts by weight of ammonia, and, therefore, as these 
figures are to each other so is 50, the actual Aveight of ammonium 
chloride used, to the weight of ammonia obtained. 

Describe the process of preparing ammonia from ammonium 
chloride. How is the gas collected? What is the appearance of 
ammonia? What is its odor? What effect does it produce upon 
breathing? What about its weight? How^ is this shown? Ex- 
plain the use of ammonia for the purpose of making ice. Does 
ammonia burn? How does water act upon it? 

What is " spirits of hartshorn "' ? " household ammonia " ? 

How is nitric acid formed in nature? 

How is nitric acid obtained from saltpetre? Express in an 
equation what takes place. Describe the apparatus used, and 
give the reasons for the arrangement of the apparatus. 

What is the appearance of pure nitric acid? What takes place 
when it is boiled? when the sun shines directly upon it? 

What is ordinary commercial nitric acid? How is strong nitric 
acid made? How does strong nitric acid act? Why do substances 
burn in strong nitric acid? Describe some experiments which illus- 
trate the power of nitric acid. What does the nitric acid give up 
to the substances upon which it acts? 

What does nitric acid give up Avhen a metallic element acts 
upon it ? Describe what further takes place, and why. 

What is aqua regia, and why has it received this name? 

What compounds does nitrogen form with oxygen? How does 
this series illustrate the law of multiple proportions? What is 
the law of multiple proportions? 

How is nitrous oxide formed? How is it usually prepared? 
Give the equation representing the action^ and state what it 
means. 



QUESTIONS AND PROBLEMS. 263 

What are the properties of nitrous oxide? its uses? 

How is nitric oxide made ? What takes place when it is brought 
in contact with the air? Why is the gas red which first appears 
in the flask used in making nitric oxide? and why does it after- 
wards become colorless? Give the equations which represent 
what takes place when nitric acid acts upon copper, and explain 
what they mean. 

How is nitrogen peroxide formed? What are its chief proper- 
ties? For what is it used? 

CHAPTER X. 

What is meant by saying that oxygen belongs to a family of 
elements ? 

In what form does chlorine occur in nature? in what quantity? 
What are all the chlorine compounds with which we have to deal 
made from? 

What two steps are necessary in order to get chlorine out of 
sodium chloride or common salt? What resemblance is there be- 
tween the process for making hydrochloric acid from common 
salt and that of making nitric acid from sodium nitrate? What 
is formed besides hydrochloric acid and nitric acid in each case? 

How is chlorine made in the laboratory? Why is this method 
not well adapted to the commercial manufacture of chlorine? 

Describe Deacon's process for the manufacture of chlorine. 

Describe Weldon's process for the manufacture of chlorine. 

Describe the electrolytic process for the manufacture of chlorine. 

Describe accurately the method of making chlorine used in the 
laboratory. How is the chlorine collected? What takes place 
when powdered antimony is introduced into chlorine? copper foil? 
flowers and calico? 

AVhat is the appearance of chlorine? its odor? its action upon the 
throat and nose? Is it heavier or lighter than air? What is its 
action upon water? What is bleaching? 

What is disinfection? What is " bleaching-powder " ? What 
other name has it? Why is it valuable as a disinfecting agent? 

Compare the action of hydrogen on oxygen and on chlorine. 
What are the products? What are chlorides? 

What is the simplest way of forming hydrochloric acid? What 
difference is there between the action of a mixture of chlorine and 
hydrogen and a mixture of hydrogen and oxygen? What art is de- 
pendent upon chemical changes caused by light? Describe the 
method of preparing hydrochloric acid. Give the equation express- 
ing the action, and state what it means. 

If 40 grams of common salt are used, how much hydrochloric 
acid and how much sodium sulphate will be obtained? 

How is the hydrochloric acid collected? W^hat are the properties 
of hydrochloric acid? Give a connected account of all that you 
learned about it in Experiment 65. How can the composition of 
hydrochloric acid be determined? What is the composition? 
What happens to hydrochloric acid when it is treated with a 



264 THE ELEMENTS OF CHEMISTRY. 

metallic element like zinc? when treated with an oxide like zinc 
oxide? When treated with substances which give up oxygen 
readily ? 

How are the chief compounds of chlorine hydrogen, and oxygen 
obtained? What is potassium chloride? potassium hypochlorite? 
potassium chlorate? What takes place when these compounds are 
treated with sulphuric acid? Express the reactions by equations, 
and show how the reactions resemble one another. Compare the 
reactions with that which takes place when sulphuric acid acts 
upon sodium or potassium nitrate. 

To which of the substances above mentioned is " bleaching-pow- 
der" allied? 

In what way does the series of compounds of chlorine with hydro- 
gen and oxygen illustrate the law of multiple proportions? 

CHAPTER XI. 

What takes place when an acid and a base are brought together? 

W^hat are alkalies? Mention some common acids; some common 
bases. How can you conveniently tell whether a substance is an 
acid or a base? 
„ What did you learn in Experiments QQ and 67? 

How can you determine what is fonned when an acid acts upon 
a base? What is formed when hydrochloric acid acts upon caustic 
soda? nitric acid upon caustic soda? sulphuric acid upon caustic 
soda? hydrochloric acid upon caustic potash? nitric acid upon 
caustic potash? sulphuric acid upon caustic potash? 

What do the experiments performed teach in regard to the action 
of acids upon bases? 

What is formed when a metallic element acts upon an acid? 

What is an acid? a base? a salt? 

What is a metal? 

Of what importance is water in these reactions? 

What is solution? What kinds of solutions are there? What 
are electrolytes? non-electrolytes? What are ions? How do acids, 
bases, and salts dissociate in solution ? Upon what does the extent 
of electrolytic dissociation depend? 

What is the difference between ions and atoms? 

Define acids and bases in terms of the theory of electrolytic dis- 
sociation. 

What is "hydroxyl"? 

Explain neutralization in terms of the theory. 

Explain the use of the syllables ic and oiis in naming acids; of 
hypo and per. Give the names and symbols of the compounds of 
chlorine, hydrogen, and oxygen. 

How are bases named? 

Explain how salts are named. What is the name and formula of 
the potassium salt of hypochlorous acid? of perchloric acid? of 
chloric acid? of nitric acid? 

What are the salts of hydrochloric acid called? Why? 

What connection is there between acid properties and oxygen? 



QUESTIONS AND PROBLEMS, 265 



CHAPTER XII. 

What takes place when animal and vegetable substances are 
heated to a high temperature? Why is this? What takes place 
when they are heated in the air? 

Give a familiar example of the process of destructive distillation. 
For what purpose is coal distilled? wood? 

What are the principal forms in which carbon occurs in nature? 
Mention some of the most common compounds of carbon. 

What two forms of pure carbon are there? 

Where are diamonds found, and what is the general appearance 
of a diamond when first found? How have diamonds been made 
artificially? 

How can graphite be made? Compare graphite and diamond, 
stating the properties of each. By what other names is gi^aphite 
known? What are its uses? 

Wliat is amorphous carbon? 

Describe the process by which charcoal is made. 

Compare the properties of charcoal with those of diamond and 
gi'aphite. 

What is coke, and how is it obtained? lamp-black? bone-black or 
animal charcoal? 

What are charcoal filters used for? AMiat are bone-black filters 
used for? 

What is the object of charring piles which are exposed to the 
action of air and water? 

What diflferent kinds of coal do we distinguish between? ^Miat 
is lignite? peat? 

How was coal formed? 

What are the chief products of the destructive distillation of 
coal? Are hard or soft coals used in the manufacture of illummat- 
ing-gas ? Why ? 

How can it be proved that diamond, graphite, and charcoal con- 
sist only of the element carbon? What common properties have 
the different forms of carbon ? 

What is meant by the name allotropy? 

How can we form an idea in regard to the reason why one and 
the same thing can appear in different forms? 

Compare the chemical conduct of carbon with, that of the other 
elements thus far considered. 

TMiat is formed when carbon combines directly with oxygen? 
How can this be proved? How can we easily recognize carbon 
dioxide ? 

Explain what takes place when a mixture of charcoal and cop- 
per oxide is heated: when a mixture of white arsenic and charcoal 
is heated. Is there any resemblance between the action of hydro- 
gen and of charcoal on heated copper oxide? 

Why is carbon called a reducing agent? 

What important use is made of charcoal as a reducing agent ? 



266 THE ELEMENTS OE CHEMISTRY. 



CHAPTER XIII. 

What are hydrocarbons? Are these easily formed in the labora- 
tory? Under what circumstances are they easily and abundantly 
formed ? 

What is petroleum? Why must it be refined before it is fit for 
use in lamps? How is it refined? What is the product called? 

What are some of the light products obtained when petroleum is 
refined? What is paraffin? 

Give the names and symbols of the four simplest hydrocarbons 
contained in petroleum. 

What is meant by homology, and an homologous series? 

Give the names and symbols of the first three members of the 
ethylene series. 

Give the names and symbols of the first two members of the 
acetylene series. 

Give the names of the first three members of the benzene series. 

Where is marsh-gas found, and under what circumstances is it 
formed ? What are the final products of the oxidation of vegetable 
matter? What is the chief product of the reduction of vegetable 
matter ? 

Of what importance is the occurrence of marsh-gas in coal-mines ? 

How is marsh-gas made in the laboratory? 

What are the properties of marsh-gas? 

How is ethylene obtained, and what are its properties? What 
other name has it? 

How is acetylene formed, and what are its properties? 

Describe in brief the method of making coal-gas. 

What is coal-tar? Mention some of the products obtained 
from it. 

What is the principal compound of carbon and oxygen? 

Where and in what forms is carbon dioxide found? 

What processes which are constantly taking place give rise to the 
formation of carbon dioxide? 

How is carbon dioxide most easily made? Describe the process 
accurately. Express the action by means of a chemical equation, 
and state what it means. 

What are the properties of carbon dioxide? 

Why does not carbon dioxide burn? 

What is meant by the statement, " Carbon can do chemical 
work"? What resemblance is there between a piece of carbon 
and an elevated body of water? 

What is soda-water, and how is it made? 

What connection is there between the breathing process and 
carbon dioxide? Is carbon dioxide poisonous? 

Why is the air in badly ventilated rooms injurious? 

Why is carbon dioxide apt to be found in old wells? How can 
it be detected if present in large quantity? 

What is choke-damp, and what does the name come from? 

Of what importance to plants is the carbon dioxide in the air?* 



QUESTIONS AND PROBLEMS. 267 

Of what importance is it to animals? What resemblance is there 
between tlie food of animals and the fuel burned in stoves? 

How does the carbon of animals and plants get back into the 
air again? 

In what way is all life directly dependent upon the sun? 

How are carbonates formed? What is the composition of 
sodium carbonate? of potassium carbonate? What, then, is the 
composition of carbonic acid? What takes place when carbonic 
acid is set free from carbonates? 

What takes place when carbon dioxide acts upon potassium hy- 
droxide? upon calcium hydroxide? Give the equations represent- 
ing the action, and name the products. 

What takes place when carbon dioxide is passed into lime- 
water until no further action is observed? What change occurs 
when the solution thus obtained is boiled? 

What are hard waters? How are they formed? Why do we 
make the distinction between temporary and permanent hard- 
ness? WTiat objection is there to hard waters? 

How is carbon monoxide formed? Explain its formation in 
open grate fires. What is the blue flame at the top of a coal 
fire due to? 

Why is the use of water-gas sometimes objected to? 

How is carbon monoxide made? What are its properties? 

"V^Tiat danger is there connected with the use of coal stoves? 
Why is smouldering charcoal a dangerous thing to have in a 
room? 

Why is carbon monoxide a good reducing agent? 

Of what importance is it in the reduction of iron from its ores? 

What is a flame? What is the difference between a candle and 
a lamp? 

How can it be shown that when a burning gas is cooled down 
it is extinguished? 

Explain the construction of the miner's safety lamp, and the 
reason for its use. 

Why do some flames give light and others not? 

How are cyanides formed? What is yellow prussiate of potash, 
and how is it made? What is potassium cyanide? How is 
cyanogen made? What are its properties? 

Where is prussic acid found? How is it made? What are its 
properties? 



CHAPTEK XIY. 

What are the two principal laws governing chemical action? 

Do we know why substances combine according to the laws of 
definite and multiple proportions? 

What is an hypothesis? a theory? 

What theory has been suggested to explain the laws of definite 
and multiple proportions? 



268 THE ELEMENTS OF CHEMISTRY. 

Show how this theory accounts for the facts. 

What is meant by the atomic weights? 

What is meant by the expression molecule? 

What are the symbols of the elements intended to represent? 
the symbols of compounds? 

Explain in full what the symbols HXO3, H0SO4, XH3, CH^, and 
CO2 are intended to represent? ^ATiat relation is there between 
the weight of a molecule and the weights of the atoms of which it 
is made up? 

What is Avogadro's hypothesis? 

How does AA^ogadro's hypothesis help us to determine the rela- 
tiye weights of the molecules of gaseous subtances? 

How are the atomic weights determined from the molecular 
weights? 

What difference is there between chlorine, oxygen, nitrogen, 
and carbon as shown by the symbols of their compounds with 
hydrogen? What is meant by the yalence of an element? 

^Yhat is meant by a uniyalent element? a biyalent element? a 
triyalent element? a quadriyalent element? Barium forms the 
compound BaCL; what is the yalence of barium? Sodium forms 
the compound NaCl; what is the yalence of sodium? 

In the formation of potassium nitrate from nitric acid, how is 
the yalence of potassium shown? When a biyalent element like 
calcium forms a salt with nitric acid, how does the displacement 
of hydrogen take place? Calcium is biyalent. ^^liat is the sym- 
bol of its salt with sulphuric acid? Explain this. ^Miat is the 
symbol of the sodium salt of sulphuric acid? "SAHiat does this 
show with regard to the yalence of sodium? 

If magnesium, Mg, is biyalent, what is the symbol of its sul- 
phate? of its nitrate? of its chloride? of its oxide? 

What is the basis for the distinction between acid-forming and 
base-forming elements? Giye examples of the two classes. What 
are these classes sometimes called? 

"\"\liat is meant when we speak of a family of elements? 

'V\niat are the families of acid-forming elements? 



CHAPTEE XV. 

Name the members of the chlorine family. 

"Why is fluorine included in this family? 

In what forms does bromine occur in nature? 

How is bromine obtained from sodium bromide? Giye the 
equations representing the steps which must be taken, and ex- 
plain what is meant by them. 

^^Tiat are the properties of bromine? "What are the chief dif- 
ferences between bromine and chlorine? 

What is hydrobromic acid, and how is it formed? What differ- 
ence is there in the conduct of common salt and of potassium 
bromide towards sulphuric acid? How is this explained? 



QUESTIONS AND PROBLEMS, 269 

What compounds docs bromine form with hydrogen and 
oxygen ? 

In what forms does iodine occur in nature? How is it obtained 
in Scothmd and Fi'ance? What is kelp? 

How is iodine obtained from sodium iodide? Give the equa- 
tions representing the action, and explain what they mean. 

What are the properties of iodine? Compare chlorine, bromine, 
and iodine, stating the points of resemblance and difference. 

How can you easily tell whether a subtsance is an iodide or 
not? Why does not potassium iodide turn starch-paste blue? 

How is hydriodic acid obtained? How does it differ from 
hydrochloric and hydrobromic acids? ^'Miat takes place when 
potassium iodide is treated with sulphuric acid? 

In what forms does fluorine principally occur in nature? How 
is it obtained? What are its properties? 

How is hydrofluoric acid made, and what are its properties? 
Give the equation representing the action of sulphuric acid on 
fluor spar? What use is made of hydrofluoric acid? Can the sub- 
stance be kept in glass bottles? 

What analogy is there between chlorine, bromine, and iodine, 
as far as the compounds which they form are concerned? 

What relation is there between the atomic weights of chlorine, 
bromine, and iodine? 

CHAPTER XVI. 

Name the members of the sulphur family. Whj has sulphur 
been knoAvn for a long time? Where is it found in nature? 
WTiat is the chief source of the sulphur of commerce? Name 
some of the principal compounds in which sulphur occurs in 
nature. 

Describe the process by which sulphur is extracted from its 
ores. 

How is crude brimstone refined? A^liat is the difference be- 
tween " flowers of sulphur " and " stick sulphur " ? Give the 
properties of sulphur. ^"Miat changes does it undergo when it is 
distilled? 

In what two forms can sulphur be obtained? How can it be 
thus obtained? How do the two forms differ from each other? 

How does sulphur act when heated in the air? 

What are sulphides? How are they formed? 

Can sulphur and hydrogen be made to combine directly? AAHiat 
is formed? AMiere is this compound found in nature? Under 
what conditions is it formed? 

How is hydrogen sulphide made in the laboratory? Explain 
what takes place when sulphuric acid is used; when hydrochloric 
acid is used. How is the substance collected? What are its 
properties? How does it behave towards water? towards metals? 
What takes place when it is passed over heated iron? Is there 
any resemblance between this action and that which takes place 



2 70 THE ELEMENTS OF CHEMISTRY. 

when steam is passed over heated iron? Express both acts by 
chemical equations. 

What takes place when hydrogen sulphide is passed through 
solutions containing metals in the form of soluble salts? 

How can hydrogen sulphide be used in chemical analysis? 

What is formed when sulphur is burned in the air? What is 
formed when sulphur dioxide takes up more oxygen? What is the 
product of the action of sulphur trioxide on water? What rela- 
tion is there between sulphurous acid and sulphuric acid? 

Where is sulphur dioxide found in nature? How is it made in 
the laboratory? Explain the reactions, giving the equations. 

What are the properties of sulphur dioxide? What uses are 
made of sulphur dioxide? 

How are sulphites made? What is the composition of sodium 
sulphite? What takes place when sodium sulphite is treated with 
sulphuric acid? with hydrochloric acid? Compare these reactions 
with those which take place when sodium carbonate, NagCOa, is 
treated with sulphuric acid and with hydrochloric acid. 

Mention some salts of sulphuric acid which are found in nature. 
How is sulphuric acid made? Explain the action of nitric oxide in 
oxidizing sulphurous acid. 

Describe the manufacture of sulphuric acid. Describe the ar- 
rangement of a leaden chamber. 

What is oil of vitriol, and how is it obtained? Ho'w does sul- 
phuric acid act upon sodium chloride? upon potassium nitrate? 

How does sulphuric acid act towards water? How does it act 
upon organic substances which contain hydrogen and oxygen? 
What change does it produce in wood? Explain the change. 

Of what importance is sulphuric acid in the arts? 

What marked difference in conduct is there between sulphuric 
acid and hydrochloric and nitric acids? 

What is a monobasic acid? a dibasic acid? 

Define acid, normal, and neutral salts. 

What is carbon bisulphide? How is it made, and what are its 
properties ? 

Why are selenium and tellurium included in the sulphur family? 

What relation is there between the atomic weights of sulphur, 
selenium, and tellurium? Has any similar relation been noticed in 
the case of other elements? 



CHAPTER XVII. 

How does phosphorus occur in nature? What is a phosphate? 

How is phosphorus made? 

What are the properties of phosphoinis ? 

Explain what takes place when phosphorus and iodine are 
brought in contact with each other. 

What is red phosphorus? How is it made from ordinary phos- 
phorus? Compare the two varieties of phosphorus. How is ordi- 
nary phosphorus made from red phosphorus? 



QUESTIONS AND PROBLEMS. 271 

Describe the changes which take place when phosphorus is 
burned in the air or in oxygen, and the product dissolved in water. 

How is ordinary phosphoric acid made? What salts does it 
form with sodium? What is normal calcium phosphate? Why is 
phosphoric acid called a tribasic acid? 

In what compounds is the element arsenic found in nature? 
What are its properties? 

What compound does arsenic form with hydrogen? What com- 
pound of nitrogen is it analogous to? How is it formed? Explain 
all that takes place in Experiments 99 and 100. 

W^liat are the properties of arsine? 

Wliat is the substance which is usually called arsenic? How is 
it obtained from the element arsenic, and from the compounds of 
arsenic with metals? W^hat are its properties? 

Explain what takes place when arsenic trioxide and charcoal are 
mixed together and the mixture heated. 

In what form does antimony chiefly occur in nature? What are 
its general properties? 

Compare stibine and arsine. 

In what forms does boron occur in nature ? How is it prepared ? 
What are its properties? 

What is borax, and from what acid is it derived? 

Mention some of the principal compounds of silicon which occur 
in nature. Is it a rare or common element? What other element 
does it resemble in some respects? 

Does silicon occur in nature in the uncombined state? How is 
the element obtained? 

Mention some of the varieties of silicic acid, and point out the 
relation which exists between them. 

Mention some of the principal varieties of silicon dioxide which 
occur in nature. 

What important manufactured product contains silicon? 

CHAPTER XVIII. 

What is meant by the name base-forming elements? What 
name is given to the elements which are not base-forming elements ? 
How does the number of base-forming elements compare with the 
number of acid-forming elements? 

What is meant by metallic properties? 

What are the chief classes of metal derivatives? 

What are minerals? 

What is meant by the term metallurgy? 

CHAPTER XIX. 

What are the alkalies, and why are they so called? 

In what form is potassium found in nature? Of what impor- 
tance is the element potassium to plants? Where does the potas- 
sium which the plants use come from ? What is left when wood is 



272 THE ELEMENTS OF CHEMISTRY. 

burned? Suppose you wanted potassium sulphate, and had only 
wood ashes and sulphuric acid, how could you get it? 

In what other forms besides those mentioned, does potassium 
occur in nature? 

How is potassium obtained from its compounds? What are its 
properties? Explain what takes place when potassium acts upon 
water. 

How is potassium iodide made? Explain the reactions. What 
takes place when potassium iodide is treated with sulphuric acid? 
W^hat is potassium iodide used fox? 

How is potassium hydroxide formed? What is its common name? 
Explain the reaction which is used in making potassium hydroxide. 
What are the properties of the hydroxide? What change does it 
undergo when exposed to the air? 

Where is saltpetre found, and under what conditions is it formed? 

Describe the saltpetre plantations. How is saltpetre used ill 
making sulphuric acid? How is it used in making nitric acid? 

Give an account of the manufacture of gunpowder, and explain 
why it acts as an explosive. 

In what form is sodium found in nature? What are its proper- 
ties? How does it differ from potassium? 

What is meant by saying that sodium is a good reducing agent? 
What is sodium amalgam, and for what is it used? 

Where and in what quantities is sodium chloride found? 

How is salt obtained from natural sources? 

What are the properties of sodium chloride? 

What are the chief uses of salt? 

What is caustic soda, and how is it obtained? 

Where is sodium nitrate found? Why can it not be used in 
making gunpowder? How can potassium nitrate be made from it? 

What is the common name of sodium sulphate? In what impor- 
tant manufacturing process is it obtained? What percentage of 
water of crystallization does it contain? What change takes place 
in it when it is left in contact with the air? Is it deliquescent or 
efflorescent ? 

Of what impoxtance is sodium carbonate? From what source 
was it formerly obtained? 

How did Leblanc come to devise a method for making sodium 
carbonate ? 

Describe Leblanc's process. 

Describe the Solvay process. 

What percentage of water of crystallization does sodium carbo- 
nate contain? 

What relation does bicarbonate of soda bear to sodium carbo- 
nate? How is it made? Explain its use in baking-powders. 

What is the substance which is commonly called phosphate of 
soda? 

What is the composition of borax ? Where is it found in nature ? 
What change takes place in borax when it is heated? Explain the 
use of borax in soldering. What is meant by saying that borax 
is an antiseptic? 



QUESTIONS AND PROBLEMS. 273 

What is water-glass, and how is it made? What is it used for? 

What action takes phice when ammonia is brought together with 
acids? What are the products when hydrochloric, nitric, and sul- 
phuric acids are treated with ammonia? Why are these substances 
included among the derivatives of the potassium family? What 
is the difference between ammonia and ammonium? 

What is sal ammoniac, and how is it chiefly obtained? Give the 
equations expressing the reactions which take place when sal am- 
moniac is treated with caustic soda and with quick-lime. 

How is ammonium sulphide made, and what is its composition? 

What relation exists between the atomic weights of the alkali 
metals ? 

What are flame reactions, and how are they used for the purpose 
of detecting substances? 

How can potassium and sodium be detected when both are 
present ? 

What is a spectrum? How can the spectrum of a light be used 
for telling what substances are in the flame? 

What are the principal parts of the spectroscope? Of what ser- 
vice has it been to chemistry? 

Tell about the discovery of helium. 

CHAPTER XX. 

Mention some of the chief compounds of calcium found in nature. 

Of what interest is calcium chloride ? How is it made ? 

What is lime? How is it made? Explain a lime-kiln. Explain 
the use of lime in making the lime-light. What change takes 
place when lime is left exposed to the air? What change takes 
place in it when it is treated with water? What is lime-water? 

What changes are produced in lime-w^ater by passing carbon 
dioxide into it? 

What is calcium carbide? How is it made? For what purpose 
is it used? 

What is bleaching-powder, and how is it made? Of what value 
is bleaching-powder? Under what conditions does it give up its 
chlorine ? 

Mention some of the principal varieties of calcium carbonate 
which are found in nature. What are stalagmites and stalactites? 

What is gypsum? Explain the use of plaster of Paris. 

Explain the difference between permanent and temporary hard- 
ness of water. 

How can temporary hardness be remedied? How can permanent 
hardness be remedied? Explain the action in each case. 

What application is made of gypsum? 

What forms of calcium phosphate are found in nature? What 
is meant by the name normal calcium phosphate? 

Of what importance is calcium phosphate to plants? \^Tiat ob- 
jection is there to the use of normal calcium phosphate as a fer- 
tilizer? What is superphosphate of lime, how is it made, and 
what is it used for? 



2 74 THE ELEMENTS OF CHEMISTRY. 

Hmv is mortar made? Why do freshly plastered rooms remain 
moist so long? How can the process of drying be hastened? 

What is common glass? What is the difference between com- 
mon glass and Bohemian glass? What is flint-glass, and for what 
is it used ? 

How is colored glass made ? 

Explain how barium dioxide is used for extracting oxygen from 
the air. How is it used in making hydrogen dioxide? 

What flame reactions do calcium compounds give? strontium 
compounds? barium compounds? 

What relation exists between the atomic weights of calcium, 
strontium, and barium? 

CHAPTER XXI. 

Mention the chief compounds of magnesium which are found in 
nature. 

How is magnesium prepared ? What are its most striking prop- 
erties? 

What is magnesia? W^hat change does water effect when 
brought in contact with magnesia? 

Mention the chief forms in which zinc is found in nature. 

How is zinc obtained from its ores? 

What are the most striking properties of zinc? 

What is galvanized iron? brass? German silver? 

Explain what takes place when zinc is heated to a high tem- 
perature in the air. 

What is zinc- white ? What advantage has it over white lead ? 

What is white vitriol? In what experiments which you have 
performed has it been obtained? How is it made on the large 
scale? What are the final products of roasting zinc sulphide? 

Where and in what form does copper chiefly occur in nature? 
What is the substance known as copper pyrites? 

What takes place when an oxide of copper is heated with char- 
coal? Explain the reaction. 

What are the most striking properties of copper? What takes 
place when it is heated with nitric acid? with sulphuric acid? 

Explain the process of copper-plating. 

What are alloys? What is brass? bell-metal? bronze? 

What is the difference in composition between cuprous and 
cupric compounds? Give examples. 

What is the composition of cuprous oxide, and what is the 
name of that variety of it which occurs in nature? 

How is copper oxide made? Explain what takes place when a 
solution of caustic soda is added to a cold solution of copper 
sulphate? What change takes place on boiling? 

What is the most common salt of copper? What effect does 
heating produce upon the substance? 

In what forms does mercury occur in nature? How is it ob- 
tained from its chief compound? Why are mercury thermome- 
ters of no value in arctic regions? 



QUESTIONS AND PROBLEMS, 275 

What are the alloys of mercury called? Wliy are the zinc 
plates in galvanic batteries amalgamated? 

How is mercuric oxide formed? For what has it been used in 
experiments which you have performed? 

What is calomel, and how is it obtained? For what is it used? 

What is corrosive sublimate, and how is it manufactured? 
What objection would there be to having a little corrosive sub- 
limate mixed with the calomel which is used in medicine? 

In what form does silver occur in nature? Explain how silver 
is extracted from galenite: (1) by Pattinson's process; (2) by 
Parker's method; (3) by the amalgamation process. 

What action do air and water have upon silver ? Why do silver 
coins, etc., carried in the pockets become dark-colored? Why do 
silver spoons used in eating eggs become tarnished? (see near the 
bottom of page 153.) 

Wliy is not pure silver used in making coins? What is used? 

How is silver-plating accomplished? How are mirrors made? 

How is silver nitrate made? Why is this salt used in making 
indelible inks? How can stains made by silver nitrate be re- 
moved ? 

Explain all the chemical processes made use of in Experiment 
117, for the purpose of making pure silver nitrate from a silver 
coin. What change takes place in silver chloride when it is ex- 
posed to the light? in silver bromide? in the iodide? 

What example have we already had to deal with which show^ed 
that light can produce chemical changes? 

Explain in brief the chemical changes upon which the art of 
photography is based. 

CHAPTER XXII. 

Mention some of the principal compounds of aluminium which 
occur in nature. 

How is aluminium made? 

What are the most important properties of aluminium? How 
does its weight compare with that of the metals in common use? 
What advantage does it possess over iron? 

What is aluminium bronze, and how is it made? How is alu- 
minium used in welding? 

What are the forms of aluminium oxide found in nature? How 
can the oxide be made in the laboratory? 

What is ordinary alum? What are the alums? Give examples. 
What relation do they bear to sulphuric acid? 

What uses are made of alum? 

What is the principal silicate containing aluminium? How 
does the element potassium get into the soil? Where does clay 
come from? Would you expect to find loose soil mostly on the 
tops of mountains or in valleys? Why? What is kaolin? 

What is porcelain? Explain the process of glazing. 

What is ultramarine, and how is it made? 



276 THE ELEMENTS OF CHEMISTRY. 

Mention the chief compounds of iron ^Yhich are found in nature. 
Where is iron found in the uncombined state? 

Explain the process of extracting iron from its ores. What is 
a flux? What is slag? 

What is pig-iron? cast-iron? wrought-iron? How is cast-iron 
converted into wrought-iron? What is steel? How is steel made? 

What are the properties of pure iron? Explain the change 
which iron undergoes in moist air. What is given off when iron 
is dissolved in hydrochloric acid? 

AAliat is the difference in composition between the ferrous and 
ferric compounds? Give the formulas of ferrous and ferric sul- 
phates, ferrous and ferric oxides. How could we decide whether 
the formula FeCL or FcoCl^ is the correct one for ferrous chloride? 

How are ferrous compounds converted into ferric compounds? 
Why is the change hastened by adding nitric acid? 

How is ferrous chloride made ? Explain the changes which take 
place when caustic soda is added to its solution, and the mixture 
is allowed to stand in contact with the air; when the solution is 
boiled with a few drops of nitric acid. How can ferric chloride 
be converted into ferrous chloride? 

What is copperas, and what other names has it? What is it 
used for? What are some of the different kinds of ink? 

Compare the formula of iron-alum with that of ordinary alum. 

What is the principal variety of ferric oxide? What is rouge, 
and how is it made? What is the composition of loadstone? 
Under what circumstances is this oxide formed? 

How is ferrous sulphide made? For what has it been used in 
experiments already performed? 

What is iron pyrites? What changes take place in it when it 
is heated in an open vessel? 

In what forms is nickel found in nature? Why is nickel used 
for plating other metals and for making coins? 

In what forms is cobalt found in nature? ^Vhat are cobalt 
compounds principally used for? What is smalt? What is cobalt 
ultramarine ? 



CHAPTER XXIII. 

What is the chief compound of manganese found in nature? 
What other compounds with oxygen does manganese form? 

What is the chief natural compound of chromium? 

What is potassium chromate, and how is it made? What is 
potassium bichromate, and how is it made? Explain the relation 
which exists between potassium chromate and potassium bichro- 
mate. How is potassium bichromate converted into potassium 
chromate? 

What takes place when potassium chromate or bichromate is 
treated with hydrochloric acid? 

What is chrome-yellow? How is it made? 



QUESTIONS AND PROBLEMS. 277 

What is chrome-alum? Explain its relation to the other alums 
which have been mentioned. 

In what form does the element uranium occur in nature? 

In what form does bismuth occur in nature, and how is it ob- 
tained from its ores? 

What is fusible metal? Wood's metal? 

What is formed when bismuth is burned in the air? 

What is the chief salt of bismuth? 

CHAPTER XXIV. 

In what compounds does lead occur in nature? 

How is lead extracted from its ores? 

What are the chief properties of lead? Explain the formation 
of the "Arbor Saturni." 

What objection is there to the use of lead pipes for conveying 
water for drinking purposes? 

What compounds does lead form with oxygen? What takes 
place when lead is heated in the air? 

What advantage is taken of this fact in separating lead and 
silver? 

What is red lead? What other name has it? What change 
does nitric acid effect in it? 

What is lead peroxide? What is formed when hydrochloric acid 
acts upon lead peroxide? 

How could you get the sulphate, chloride, and chromate of lead? 

What is white lead? Why does white lead turn black and zinc- 
white not? 

In what form does tin chiefly occur in nature? How is the metal 
obtained from the ore? 

What is tin-foil? What effect does air have on tin at the or- 
dinary temperatures? What effect does nitric acid produce on 
tin? 

What is tin- ware? What danger is there in the use of inferior 
tin-ware? What are pins made of? 

What is solder? britannia? bronze? bell-metal? Explain the 
process of soldering. What objection is there to the use of solder 
in closing tin cans containing things which are to be eaten? 

What is the difference in composition between stannous and 
stannic compounds? 

What is tin salt? What is it used for? What is mosaic gold? 

In what form does platinum occur in nature? Where is it chiefly 
found? How is it obtained from its ores? 

What are the most striking properties of platinum? 

For what purposes is platinum used? 

In what form does gold occur in nature? 

How is it usually extracted from its ores? 

What are its most striking properties? 

Why is not pure gold used in making gold ware and coins? 
What is 20-carat gold? What is the composition of the standard 
gold coin of the United States? 



278 THE ELEMENTS OF CHEMISTRY. 



CHAPTER XXy. 

What was the first meaning of the name organic chemistry ? inor- 
ganic chemistry? What does organic chemistry mean now? 

Mention some of the principal forms in which carbon occurs in 
nature ? 

What takes place when coal is distilled? 

What takes place when wood is distilled? 

What takes place when bones are distilled? 

What is meant in general by fermentation? What is the best 
known example of fermentation? 

Mention some of the principal classes of compounds of carbon. 

How is methyl alcohol formed ? What other name has it ? What 
are its chief properties? 

How is ordinary alcohol made ? Explain what took place in Ex- 
periment 127. 

What change takes place in sugar when it undergoes fermenta- 
tion? What causes the change in the sugar? Why do fruit- juices 
lose their sweetness when exposed to the air? 

Mention some other kinds of fermentation besides alcoholic fer- 
mentation. 

How is alcohol obtained from fermented liquids? What is fusel 
oil? 

What are the chief properties of ethyl alcohol? 

What are the chief uses of alcohol? 

What is glycerin? How is it obtained? What are its chief 
properties ? 

What is formic acid, and where is it found in nature? What 
are its chief properties? 

What is acetic acid? What is "mother of vinegar"? How is 
acetic acid made? Whence come the names pyroligneous acid and 
wood-vinegar? 

What are the chief properties of acetic acid ? For what purposes 
is it used? What are the principal salts of acetic acid? 

What are the fatty acids? Mention some of the principal fatty 
acids. What is such a series as that of the fatty acids called? 

Of what interest is butyric acid? palmitic acid? stearic acid? 

What are soaps? How are they made? How does soap act in 
washing ? 

What happens when soap is added to a hard water ? Why do the 
hands feel sticky when we attempt to wash them in hard water? 

What connection is there between soap and civilization? How is 
soft-soap made? What connection is there between the manufac- 
ture of sulphuric acid and sodium carbonate and that of soap? 

What is the composition of oxalic acid? Where and in what 
form is it found in nature ? How is it manufactured ? For what is 
it used? 

What is the composition of lactic acid? How i& it formed? 

Where is malic acid found in nature? 



QUESTIONS AND PROBLEMS, 279 

Where is tartaric acid found in nature? What is "cream of 
tartar," and under what circumstances is it formed? 

Where is citric acid found in nature? How is it prepared? 

What is ordinaiy ether? How is it made? 

What is meant by the word ansesthetic? 

What is the action of an alcohol upon an acid? What is the 
product called? WTiat class of substances do the alcohols act like? 
Compare the action of nitric acid upon alcohol and upon caustic 
potash. 

What is meant by saponification? 

What are fats? Explain what takes place when fats are treated 
with an alkali. 

What does butter consist of? oleo-margarin ? 

What connection is there between the flavors of fruits and 
ethereal salts? 

What is nitroglycerin? To what class of substances does it be- 
long? What is dynamite? 

What relations exist between the hydrocarbons of the marsh- 
gas series and the simplest alcohols and acids? 

What is an alcohol? 

What similarity is there between aluminium hydroxide and 
glycerin ? 

W^hat is meant by the expression radical or residue? 

What common acid are the organic acids related to? 



CHAPTER XXVI. 

What are the carbohydrates? 

Where is dextrose found? What other names has it? 

How is dextrose formed? What relation exists between it and 
cane-sugar? between it and starch? 

Describe the process used in the manufacture of glucose. 

What are the chief properties of glucose? How does it differ 
from cane-sugar? How can alcohol be obtained from it? How 
lactic acid? 

What is fructose? What relation exists between it and cane- 
sugar ? 

Where is cane-sugar found in nature? 

Describe the process of sugar-refining. 

What is molasses? What are the chief properties of sugar? 
What is caramel? invert-sugar? What is the action of yeast 
upon cane-sugar? 

What is sugar of milk? What are the constituents of cow's 
milk? How is cheese made? What is it? How is sugar of milk 
obtained from milk? What does the process of souring of milk . 
consist in? 

Of what importance is cellulose in the vegetable kingdom? 
What takes place when cellulose is treated with concentrated 
sulphuric acid and boiled? What is gun-cotton? collodion? What 



2 8o THE ELEMENTS GF CHEMISTRY, 

is collodion used for? AMiat is celluloid? What is paper? De- 
scribe the process of paper-making. 

In what forms is starch found in nature? Describe the manu- 
facture of starch. What is starch-paste? What change is effected 
in starch by dilute acids and ferments? 

What are the chief constituents of flour? 

'V^^at causes bread to rise? 

What is meant by the name "aromatic compounds"? 

What is nitrobenzene, and how is it made? 

How is aniline made? What is magenta? AATiat are the aniline 
dyes? 

What is carbolic acid? 

What is the oil of bitter almonds? Where is it found in nature? 
What is it used for? 

What is the source of benzoic acid? "SA^iat are balsams? Give 
some examples. 

Where is gallic acid found? How is it prepared? 

Where does tannic acid occur? For what is it used? 

What does the process of tanning consist in? 

In what form and where does indigo occur in nature? 

What is naphthalene? anthracene? What is the chief use of 
anthracene ? 

What is alizarin? How is it made? 

What are the glucosides? Whd^t examples have already been 
mentioned? Of what importance is myronic acid? 

What are the alkaloids? What simple inorganic compound do 
they resemble? What is the source of quinine? cocaine? nico- 
tine? morphine and narcotine? 



INDEX. 



Acetylene, 118, 119 
Acid, acetic, 230, 234 

benzoic, 252 

bichromic, 220 

boracic, 169 

boric, 169 

bromic, 145 

butyric, 235, 240 

carbolic, 251 

carbonic, 127 

chloric, 92, 93 

chlorous, 93 

chromic, 220 

citric, 238 

formic, 234 

gallic, 252 

hydriodic, 146 

hydrobromic, 144 

hydrochloric, 87, 93 

hydrocyanic, 134, 252 

hydrofluoric, 147 

hypobromous, 145 

hypochlorous, 92, 93 

lactic, 238 

malic, 238 

metaphosphoric, 166 

metastannic, 225 

myronic, 254 

nitric, 72, 75 

nitrous, 72 

oleic, 240 

orthophosphoric, 166 

oxalic, 237 

palmitic, 235, 240 

perchloric, 93 

phosphoric, 166 

propionic, 235 

prussic, 134 



Acid, pyroligneous, 230, 234 

silicic, 171 

stearic, 235, 240 

sulphuric, 156, 158 

sulphurous, 156, 157 

tannic, 253 

tartaric, 238 

tetraboric, 170 

valeric, 235, 240 
Acids, 50, 97, 100, 101, 234, 242 

characteristics, 97 

dibasic, 161 

fatty, 235 

monobasic, 161 

names of, 101 

organic, 234, 237, 242 

tribasic, 166 
Acid-forming elements, 141, 173 
Agate, 171 
Air, 17, 41 

liquid, 41 
Alcohol, ethyl, 231 

methyl, 231 
Alcohols, 230, 231, 241 
Alizarin, 254 
Alkalies, 94, 177 
Alkaloids, 254 
Allotropy, 112 
Alloys, 202 
Allylene, 118 
Alum, 210 

ammonia, 210 

chrome, 220 

iron, 217, 221 

potassium, 210, 221 

sodium, 210 
Aluminium, 209 

bronze, 210 

281 



252 



INDEX. 



Aluminium, hydroxide^ 210 

oxide, 210 

silicates, 211 

sulphate, 210 
Amalgamation process, 205 
Amalgams, 204 
Amethyst, 171 
Ammonia, 71 

formation, 65 

in air, 21 

in gas liquor, 72, 111 

preparation, 73 

properties, 74 

water, 74 
Ammonium, 186 

chloride, 72, 186 

salts, 186 

sulphide, 187 
Amygdalin, 251 
Analysis, 155 
Aniline, 251 

dyes, 251 
Anthracene, 230, 254 
Anthracite coal, 110 
Antimony, 169 
Apatite, 164, 190, 194 
Aqua regia, 79 
Arbor Saturni 223 
Argon, 21, 42 
Aromatic compounds, 250 
Arsenic, 166 

trioxide, 168 
Arsine, 167 
Asbestos, 198 
Atomic theory, 136 

weights, 137 

determination of, 138 
Atoms, 136 
Avogadro's hypothesis, 137 

Baking-powdees, 185 
Balsams, 252 
Barium, 196 

chromate, 220 

dioxide, 70, 196 

oxide, 196 

sulphate, 150 
Base-forming elements, 141, 173 
Bases, 94, 97, 100, 102 

names of, 102 
Bell-metal, 202 



Benzene, 118, 230, 250 
Benzine, 117 
Benzoic aldehyde, 251 
Bessemer process, 214 
Bicarbonate of soda, 185 
Bismuth, 221 

nitrate, 221 

oxide, 221 
Bituminous coal, 110 
Blast furnace, 213 
Bleaching, 86, 157 

powder, 92, 192 
Blow-pipe, oxyhydrogen, 61 
Bone-ash, 164, 194 
Bone-black, 109, 230 
Bone-oil, 230 
Borax, 170, 185 
Boron, 169 

crystallized, 170 

oxide, 170 
Brass, 199, 202 
Bread-making, 250 
Breathing, 27, 124 
Britannia, 225 
Bromine, 143 
Bronze, 202 
Burning in air, 18, 28 

in oxygen, 27 
Butane, 117 
Butter, 240 
Butylene, 118 

Cadmium, 198 
Caesium, 189 
Calamine, 199 
Calcium, 190 

carbide, 120, 192 

carbonate, 128, 190, 193 

chloride, 190 

fluoride, 147, 190 

hydroxide, 191 

hypochlorite, 192 

light, 62 

oxide, 191 

phosphate, 190, 194 

sulphate, 150, 190, 193 
Calcspar, 193 
Calomel, 204 
Cane-sugar, 244, 245 
Caramel, 246 
Carbohydrates, 244 



INDEX. 



283 



Carbon, 105 

as food for plants, 126 

dioxide, 121 

disulphide, 1G2 

monoxide, 129 

silicide, 171 
Carbonates, 127 
CarboTundum, 171 
Carnallite, 198 
Carnelian, 171 
Casein, 247 
Cast-iron, 213 
Celluloid, 248 
Cellulose, 244, 247 
Chalk, 190, 193 
Charcoal, 107 

animal, 109 

reduction by, 114 
Chemical action, 11 

changes, 2 

energy, 31 

work, 31 
Chemistry, 2 
Chloride of lime, 92, 192 
Chlorides, 87, 103 
Chlorine, 83 

acids, 92, 93 

bleaching by, 86 

comparison with bromine 
and iodine, 148 

Deacon's process, 84 

electrolytic process, 85 

occurrence, 83 

preparation, 83 

properties, 86 

Weldon's process, 85 
Choke-damp, 126 
Chromates, 219 
Chrome alum, 220 

yellow, 220 
Chromic iron, 219 
Chromium, 219 
Cinnabar, 203 
Clay, 170, 209 
Coal, 110 
Coal-gas, 120, 230 
Coal-tar, 111, 121, 230, 250 
Cobalt, 218 
Cocaine, 255 
Coke, 108 
Collodion, 248 



Combination, chemical, 11 
Combining weights, 34, 53 
Combustion, 29 
Compounds, chemical, 9, 10 
Copper, 200 

acetate, 235 

alloys, 202 

chlorides, 202 

nitrate, 201 

oxides, 202 

plating, 201 

pyrites, 150, 200 

sulphate, 203 
Corrosive sublimate, 204 
Corundum, 210 
Cream of tartar, 185, 238 
Cryolite, 147, 209 
Cupellation, 205 
Cupric compounds, 202 
Cuprous compounds, 202 
Cyanides, 133 
Cyanogen, 133 

Deacon's peocess, 84 

Decomposition, 11 

Definite proportions, law of, 32 

Deliquescent substances, 45 

Dextrin, 244, 250 

Dextrose, 244, 250 

Diamond, 106 

Disinfection, 86 

Dissociation, 99 

Distillation, 64 

destructive, 71, 105, 230 

of bones, 230- 

of coal. 111, 230 

of wood, 230 
Dolomite, 198 
Drummond light, 62 
Dynamite, 241 

Earthenwaee, 211 
Efflorescent substances, 45 
Electrolytes, 99 
Elements, 9, 10 

classification, 141 

names, 14 

symbols, 14 
Emery, 210 
Emulsin, 252 
Epsom salt, 198 



284 



INDEX. 



Essence of apples, 240 

pineapples, 240 
Etching, 147 
Ethane, 117 
Ether, 238 
Ethereal salts, 239 
Ethers, 238 
Ethyl alcohol, 231 
Ethylene, 118, 119 
Eudiometer, 58 

Fats, 240 

Feldspar, 177. 209, 211 
Fermentation, 230, 231, 232 
Ferric chloride 215 

hydroxide, 215 

oxide, 215, 217 

sulphate, 215 
Ferrous chloride. 215, 216 

hydroxide, 215 

oxide, 215 

sulphate, 215, 216 
Fire-damp, 119 
Flame, 131 

Flame-reactions, 187, 197 
Flour, 250 
Fluorine, 147 
Fluor spar, 147, 190 
Flux, 213 
Fructose, 244, 245 
Fruit-sugar, 245 
Fusel-oil, 233 
Fusible metal, 221 

Galenite. 150, 222 
Gallium, 189 
Galvanized iron, 199 
Gas, olefiant, 119 
Gasoline, 117 
German silver, 199 
Glass, 195 
Glauber's salt, 183 
Glucose, 244 
Glucosides, 252, 254 
Gluten, 250 
Glvcerin, 233, 240, 242 
Glvcervl, 240, 242 
Gold, 227 
Granite, 209 
Grape-sugar, 244 
Graphite, 106, 107 



Gum, 244 
Gun-cotton, 248 
Gunpowder, 180 
Gypsum, 150, 190, 193 

Heat and chemical change, 

4, 30 
Heavy spar, 150 
Helium, 189 
Hematite, 212, 217 
Heptane, 118 
Hexane, 118 

Homologous series, 118, 235 
Homology, 118 
Hornblende, 198 
Hydrocarbons, 116, 231 
Hydrogen, 48 

dioxide, 70 

liquid, 54 

preparation, 48 

properties, 52, 54 

sulphide, 153 
Hydroxyl, 100 
Hypothesis, 135 

Illumixatiox, 131 
Incense, 252 
Indican, 253, 254 
Indigo, 253 
Indium, 189 
Inks, 207, 217, 253 
Invert- sugar, 247 
Iodine, 145 
Ions, 99 
Iridium, 226 
Iron, 212 

carbonate, 212 

cast, 213 

chlorides, 215 

ores, 212 

oxides, 212, 217 

pyrites, 150, 212, 217 

sulphides, 150, 153, 212, 217 

Kaolin, 211 

Kelp, 145 

Kerosene, 117 

Kindling temperature, 30 

Lactose, 247 
Lamp-black, 108 



INDEX. 



285 



Lapis lazuli, 212 
Laughing-gas, 80 
Lead, 222 

acetate, 235 

carbonate, 222, 224 

chloride, 224 

chromate, 220, 222, 224 

oxides, 223 

sulphate, 150, 222, 224 

sulphide, 222 

tree, 223 

white, 224 
Leblanc's method, 184 
Levulose, 244, 245 
Lignite, 110 
Lime, 191 

light, 62 
Limestone, 190, 193 
Litharge, 223 
Lithium, 187 
Loadstone, 217 
Lubricating oils, 117 
Luminosity of flames, 133 
Lunar caustic, 206 

Magenta, 251 

Magnesia, 199 
Magnesite, 198 
Magnesium, 198 

carbonate, 198 

hydroxide, 199 

nitride, 198 

oxide, 198, 199 

silicate, 170, 198 

sulphate, 198 
Magnetite, 212, 217 
Maltose, 244, 250 
Manganese, 219 

dioxide, 219 

oxides, 219 
Marble, 190, 193 
Marsh-gas, 117, 118 
Matches, 165 
Meerschaum, 198 
Mercuric chloride, 204 
Mercuric oxide, 204 
Mercuroiis chloride, 204 
Mercury, 203 

chlorides, 204 

cyanide, 134 

oxide, 204 



Mercury sulphide, 203 
Metallic properties, 174 
Metals, 98, 173 
Metathesis, 12 
Methane, 117, 118 
Methyl alcohol, 230, 231 
Mica, 209 
Minium, 223 
Mixture, mechanical, 9 
Molasses, 246 
Molecular formulas, 137 

weights, 137 
Molecules, 137 
Mono-sodium carbonate, 185 
Mordants, 211 
Morphine, 255 
Mortar, 195 
Mosaic gold, 226 
Moth-balls, 254 
Multiple proportions, 36, 93 
Mustard oil, 254 

Naphtha, 117 
Naphthalene, 230, 253 
Narcotine, 255 
Neutralization, 94, 100 
Nickel, 218 

hydroxides, 218 
Nicotine, 255 
Nitrates, 72, 78 
Nitric oxide, 79, 80, 158 
Nitrites, 72 
Nitrobenzene, 251 
Nitro-cellulose, 248 
Nitrogen, 39 

in air, 21, 41 

oxides, 79 

pentoxide, 79 

peroxide, 79^ 82 

preparation, 39 

properties, 40 

trioxide, 79 
Nitroglycerin, 240 
Nitrous oxide, 80, 79 
Nomenclature, acids, 101 

bases, 102 

salts, 102 
Non-electrolytes, 99 

Octane, 118 

Oil of bitter almonds, 251 



286 



INDEX, 



Oleo-margarin, 240 

Opium^ 255 

Organic chemistry, 2z9 

Osmium, 226 

Oxides, 31 

Oxygen^ 22 

preparation, 22, 42 

properties, 25 
Oxyhydrogen blow-pipe, 61 
Ozone, 69 

Palladium, 226 
Paper, 248 
Paraffin, 117 
Parker's process, 205 
Pattinson's process, 205 
Peat, 110 
Pentane, 118 
Petroleum, 106, 116, 230 
Phenol, 251 

Phosphorite, 164, 190, 194 
Phosphorus, 164 

oxide, 166 

red, 165 
Photography, 208 
Physical changes, 2 
Pig iron, 213 
Pitchblende, 221 
Plaster of Paris, 193 
Platinum, 226 

chloride, 226 
Plumbago, 106, 107 
Porcelain, 211 
Potash, 177 
Potassium, 177 

bichromate, 219 

chlorate, 92, 180 

chloride, 92 

chromate, 219 

cyanide, 133 

ferrocyanide, 133 

hydroxide, 179 

hypochlorite, 92 

iodide, 178 

myronate, 254 

nitrate, 179 

oxalate, 237 

tartrate^ 238 
Propane, 117 
Propylene, 118 
Prussiate of potash, 133 



Puddling, 214 
Pyroxylin, 248 

QUAETZ, 170, 171 
Quartzite, 170, 171 
Quinine, 255 

Radicals, 242 
Red lead, 223 
Reduction, 61, 115 
Residues, 242 
Rochelle salt, 185 
Rock crystal, 171 
Rouge, 217 
Rubidium, 189 
Ruby, 210 
Ruby copper, 200 
Rust, 214 

Safety-lamp, 132 

Safety-matches, 165 

Sal ammoniac, 72 

"Salt," 181 

Saltpetre, 179 

Salts, 98, 102 
acid, 162 
names of, 102 
neutral, 162 
normal, 162 

Sand, 170 

Saponification, 239 

Sapphire, 210 

Seidlitz powders, 185 

Selenium, 163 

Serpentine, 198 

Siderite, 212 

Silica, 170 

Silicates, 170 

Silicides, 171 

Silicon, 170 

dioxide, 170 

Silver, 204 

alloys, 206 
bromide, 208 
chloride, 208 
iodide, 208 
nitrate, 206 
plating, 206 

Slag, 213 

Slaking, 191 



INDEX, 



287 



Slow oxidation, 26 
Smalt, 218 
Soaps, 235 
Soapstone, 198 
Soda, 183 
Soda-water, 124 
Sodium, 180 

borate, 170, 185 

carbonate, 183 

chloride, 181 

hydroxide, 182 

hyposulphite, 208 

nitrate, 182 

phosphate, 185 

sulphate, 183 
Solder, 225 
Soldering, 185, 225 
Solution, 7, 66, 98 
Solvay method, 184 
Spectroscope, 188 
Spirits of hartshorn, 74 

of wine, 231 
Stalactites, 193 
Stalagmites, 193 
Stannic chloride, 226 

compounds, 226 

sulphide, 226 
Stannous chloride, 226 

compounds, 226 
Starch, 244, 249 
Stearin, 235 
Steel, 214 
Stibine, 169 
Strontium, 196 
Sugar of lead, 235 

milk, 247 
Sugar-refining, 246 
Sulphites, 157 
Sulphur, 150 

dimorphism of, 152 

dioxide, 156 

trioxide, 156, 160 
Sulphuretted hydrogen, 153 
Superphosphate of lime, 195 
Symbols, 14, 35, 38 

Tannin, 253 
Tanning, 253 
Tellurium, 163 
Thallium, 189 



Theory, 135 
Tin, 224 

oxide, 224 

salt, 226 

sulphide, 226 
Tin-stone, 224 
Toluene, 118, 230, 250 
Turkey-red, 254 

Ulteamarine, 212, 218 
Uranium, 221 

Valence, 138 
Verdigris, 235 
Vitriol, blue, 203 

green, 216 

oil of, 160 

white, 200 

Water, 44 

analysis, 46 
as a solvent, Qb 
hard, 128, 193, 236 
maximum density, 63 
of crystallization, 45 
properties, 62 
synthesis of, 58 
uses in chemistry, 67 

Water-gas, 49, 129 

Water-glass, 186 

Weldon's process, 85 

White lead, 200, 224 

Wood-alcohol, 230, 231 

Wood's metal, 221 . 

Wood- spirit, 231 

Wood- vinegar, 234 

Wr ought-iron, 214 

Xylene, 118, 230 

Zinc, 199 

blende, 199 
carbonate, 199 
method for silver, 205 
oxide, 199 
silicate, 199 
sulphate, 200 
sulphide, 199 ^ 
white, 200 ^ 



WEIGHTS AND MEASUEES. 



ENGLISH SYSTEM. 
Troy or Apothecaries' Weight, 



Pound. 


Ounces. 


Drams. 


Scruples 


;. Grains. 




Grams. 


1 


= 12 = 


96 = 


288 


= 5760 


— 


372.96 




1 = 


8 = 


24 


480 


= 


31.08 






1 = 


3 


60 


— 


3.885 








1 


20 
1 


— 


1.295 
0.0647 






Awirdupois Weight, 






Pound. 


Ounces. 


Drams. 




Grains. 




Grams. 


1 


= 16 


= 256 


rr 


7000 


=z 


453.25 




1 


= 16 


r=: 


437.5 


= 


28.328 






1 


= 


27.343 
1 


= 


1.77 
0.0647 


Gallon. 


Pints. Fl 


Imperial Measure. 
. Ounces. Fl. Drams. Minims. 


Cubic 
Centimeters. 


1 


=r 8 = 


160 = 


1280 


= 76800 


= 


4545.86 




1 = 


20 = 


160 


= 9600 


— 


568.23 






1 = 


8 


480 


= 


28.41 








1 


60 
1 cubic inch 


= 


3.55 
16.383 



METRIC SYSTEM. 
Measures of Length. 



3ter. Decimeters. Centimeters. Millimeters. 
1 = 10 = 100 = 1000 
1 == 10 = 100 
1 = 10 

1 


Inches. 

39.87100 

= 393710 

= 0.39371 

= 0.03937 


Measures of Capacity, 
Liter, Cubic Centimeters. Pints. 

1 = 1000 = 1.76 = 
1 = 0.00176 = 


Cubic Inches. 

61.0363 

0.0610 


Measures of Weight. 
Kilogram. Grams. Lbs. (Avoirdupois). 
1 = 1000 = 2.2046 = 
1 = 0.0022 = 


Grains. 
15432.00 
15.432 



CHEMISTRY 



CAIRNS'S QUANTITATIVE CHEMICAL ANALYSIS 

By Fkedekick A. Cairns. Entirely new edition^ revised and 
enlarged by Dr. E. Waller. xii-f-4i7Pp. 8vo. $2.00, «^/. 

CONGDON'S QUALITATIVE ANALYSIS 

By Prof. Ernest A. Congdon, of Drexel Institute. 64 pp. Inter- 
leaved. 8vo. 60c., 7iet. 

NICHOLSON AND AVERY ' S EXERCISES IN 

CHEMISTRY ^'^^^ outlines for the Study of Chemisiry. To 
___^____^_ accompany any elementary text. By Prof. H. H. 
Nicholson, of the University of Nebraska, and Prof. SA^1L■EL 
Avery, of the University of Idaho. 413 pp. i2mo. 6oc., net 

NOYES'S ELEMENTS OF QUALITATIVE 

ANALYSIS ^>' ^roi. Wm. A. NoYES, of the Rose Polytechnic Insti- 
^^_^^_^.^_^_ tute. x-j-qipp. 8vo. Zoz.^net. 

REMSEN'S CHEMISTRIES m- Prof. IkaRemsen, of Johns 

___«__»«_.^^^________^__ - Hopkins. {American Cicience 

Series.) 

IJLOTgZmC C\i.timstrj {Advanced), xxii + 853 pp. 8vo. %2.^o, net. 

Introduction to ClieiIlistry(y5rzV/<?r). xix + 435pp. izmo. %i.i2^net. 
In addition to its pronounced success in this country, where it is 
used in hundreds of schools and colleges, the book has passed through 
several editions in England, and has been translated into German 
(being the elementary text-book in the University of Leipsic) French, 
and Italian. 

Remsen and Randall's Experiments {for the ''Introduction''). 

50c., 7iet. 
Elements of Chemistry {Elementary^, x -f 272 pp. i2mo. 80c., net. 
Laboratory Manual {/or the " Elements''). 40c., net. 

TORREY'S ELEMENTARY CHEMISTRY 

By Joseph Torrey, Jr., of Harvard. 437 pp. i2mo. Si. 25, net. 

The Dial : *' It combines lectures and demonstrations with labora- 
tory work in a manner that commends itself strongly to our appro- 
val. ... It was time for some one to say these things, and we com- 
mend the book most heartily. The essential aim of the author is to 
restore the disciplinary value of the study, and his method is well 
w^orihy of attention." 

WOODHULL AND VAN ARSDALE>S CHEMICAL 

EXPERIMENTS ^y P^°^- J^"^' ^- ^Voodhull and M. B. V.an 
^_^^____________ Arsdale, both of Teachers' College, New York 

City. 136 pp. i2mo. 6oc., net. 

Extremely simple experiments in the chemistry of daily life. 

HFNRY HOI T Rr TO 29 west 23d st., new york 

nClNI\I V\\J\^\ ex K^yj. 373 Watasli Ave., CHICAGO 
yi| 1900 



BRITTON'S MANUAL OF THE FLORA OF THE 
NORTHERN STATES AND CANADA. 

By Director N. L. Britton of the New York Botanical Garden. 
1080 pp. 8vo. ^2.25, net. 

A comprehensive manual of over a thousand pages, containing about 4,500 
descriptions, probably one-third more than any other. It is designed to meet 
modern requirements and outline modem conceptions of the science. It is 
based on An Ilhistrated Flora, prepared by Prof. Britton in co-operation 
with Judge Addison Brown. The text has been revised and brought up to date, 
and much of novelty has been added. All illustrations are omitted, but 
specific reference has been made to all of the 4,162 figures in the Illustrated 
Flora. 

*' It is the most complete and reliable work that ever appeared in the form of 
a flora of this region, and for the first time we have a manual in which the plant 
descriptions are drawn from the plants themselves, and do not represent com- 
piled descriptions made by the early writers." — Prof. L. M. Underwood of 
Columbia. 

" This work will at once take its place as the standard manual of the region 
that it covers. It is far superior to any other work of its class ever published in 
America."— Prof. Conway MacMillan of University of Minnesota. 

" This book must at once find its way into the schools and colleges, to which 
it may be commended for the students in systematic botany." — Prof. Chas. 
E. Bessey in "Science." 

** It is nothing if it is not compact ; it is nothing if it is not up to date ; it is 
nothing if it is not the work of a master. What more can be said, save that the 
more it is used the greater the appreciation by the plant-lovers in the region 
which it covers."— Prof. Byron D. Halsted of Rutgers College. 

*' The work is well done ; and as it is the only volume which gives in a way 
suitable for students the present state of the science, it cannot fail to take its 
place as a standard work." — Prof. George Macloskie of Princeton. 

" I regard the book as one that we cannot do without and one that will hence- 
forth take its place as a necessary means of determination of the plant species 
within its range."— Prof. V. M. Spalding of University of Michigan. 

" An exceedingly valuable contribution to our botanical literature. ... It is 
convenient to handle, and the low price will help to give it a large circulation." 
—Prof. T. J. Burrill of the University of Illinois. 

UT7\]PVUPiIT>^r/^r^ 29 West 23d Street, New York 
ncINrCl nULl Cx ^vj. , 378 Watasli Avenue, CMcago 
III '02 



.^^ ■^^.. " 




O-O. 






<f :£mh^ %.^ 



,■ 0_v 







^ v^ ^-.'^m^ 




^'C^^^rS^ o>' 












^^• A^^''^/- 



^^^ s^' 



.■^ -7- 



'c*^ -;%: 



p^.° -r 



.0- 



•^/^ 


V^ 




n" 




^ 


♦- ^ 


.„:% 




'^ ° x> ,^^' 






,*^ ^^^ 



.#' 



■"oo^ 






■^>. ' 



>^^. 



.x*^' - 






■^-v 



^^ 






-n:- 

■ o 



x:^- ^ 



. \ 1 ft 






^, 









... - A 



\ 



'-^^■ 






^^ 



A' 












.s^% 









.^^ ."^.^^.^^ 



o 0' 



O^ -^rl 



V' 




'O. v= 









\0 o. 






